Picture the last food scrap you threw away. Maybe you were dumping some potato peels in the trash, or composting the outer leaves of a cauliflower. Why did you throw it away? Was it for aesthetic reasons? Did you consider any of that food inedible? Did you have patience in that moment to think of a reason to keep it? Were you out of containers to store it in? There are a multitude of reasons why food ends up in the bin, but we hope this article can make it easier to give your food (waste) another chance.

Food waste, as we’ve explored in this series on food knowledge, is one of the most urgent yet avoidable contributors to climate change. Even a single apple that goes to waste due to poor storage strategies or aesthetic imperfections represents a loss of all its embodied energy. That is to say, all the water and land used to grow it, all the energy used to transport and store it, and all of the caloric energy it could have provided to someone are squandered. At such a small scale, it’s negligible, and yet when everyone believes that throwing away food is not a big deal, it leads to enormous quantities of waste that often end up in landfills, releasing methane (a potent greenhouse gas) into the atmosphere.

Reframing Fruit Scraps

One way to reduce food waste is to rethink what you consider food. Of course, this isn’t to say that you should go around eating nut shells and parts of food that leave you with indigestion, but some foods that we are taught to discard have great flavors and health benefits. 

On the most basic level, this applies to fruits with soft peels. Your apple, pear, peach, or nectarine skins can and should be eaten, but certain dessert recipes ask you to peel them, and in those cases, you can enjoy the peel by itself or use it in tea. Beyond those four, kiwi skin adds fiber and flavor when you eat it with the rest of the fruit, and dried pomegranate and hazelnut skin can be pulverized and added to smoothies or sprinkled on meals as a supplement. But fruit scraps don’t just have to be healthy; we highly recommend making treats out of your lemon and orange rinds. Although candied citrus rinds are great dipped in chocolate or sprinkled on cakes, the ones we made were devoured before they could make it to those stages.

More unusually, banana skins make a wonderful meat substitute in some recipes, like tacos or lasagna. Watermelon rinds make good pickles, but they can also be candied by cooking them in sugar syrup. If you make your own milk alternatives at home, you can use the strained almond, oat, rice, or cashew pulp for baking by replacing some of the flour in a recipe with pulp. (Be aware that milk pulp as a flour replacement will have an effect on the moisture and gluten content, so it only works in small ratios of pulp to flour and doesn’t work for difficult pastries, like croissants.) Another unusual recipe we tried was jam made out of passion fruit rinds. By boiling the rinds, taking the skin off, and mashing them with sugar, we cooked a slightly floral and astringent spread that goes well with bread or scones.

Vegetable Scrap Recipes

It’s helpful to rethink how you treat the scraps from your vegetables, too. Make sure not to waste delicious broccoli stalks or beet greens, and definitely don’t throw out the peels of your root vegetables. When a recipe requires peeled potatoes, the peels make a crispy snack or garnish when baked with some oil. Carrot greens transform into a delicious pesto when blended with oil, garlic, sunflower seeds, and salt.

Anything hard to chew can be blended into sauces, as is the case with kale stems and pea shells, and the stems of chard can be pickled. You can even sauté the tough green ends of leeks! The leaves of cauliflower, broccoli or romanesco broccoli should be cooked and eaten as well. Fava pods can be eaten whole, by grilling or sautéing them. When we tried out this recipe, we topped the pods with lemon juice, salt, chili flakes, and mint. 

It should go without mentioning that any vegetable scraps can be made into broth. Herb stems are superb for this purpose, but celery, onions, leeks, carrots, potatoes, and celery root all provide scraps to flavor your broth. Sometimes, there isn’t enough waste to produce broth, so these scraps can be stored in the freezer while you collect enough.

Similarly to broth, parts of some foods can be added to teas or infused on their own. This is most true for leaves, especially artichoke, persimmon, and strawberry leaves, and for dried or fresh citrus rind. 

Other Food Scrap Uses

Food scraps have purposes beyond just culinary! When making a vinegar-based cleaning solution for your house, lemon, orange and grapefruit rinds add a nice aroma. Banana skins serve as aphid repellents when they are chopped up and buried a couple inches deep around the base of a plant, and have anti-inflammatory properties when used on irritated skin. Coffee grounds and oat, almond and rice milk pulp are great body exfoliants, with rice and oat pulp having additional soothing properties when used on facial skin.

Many food scraps can be used to regrow foods, and these experiments double as educational projects as well. Root vegetables can be regrown by placing the tops of the root in water until new leaves begin to grow, at which point they can be planted in soil. Ginger pieces the size of an inch can be planted directly, and in very little time they will grow more ginger. Long, green vegetables such as celery, lemongrass, leeks, and green onions can be regrown by placing one inch of the bottom part of the plant (not counting the length of the roots) in a tray or glass of water until it begins to grow again. They can then be planted in soil. Leafy vegetables such as lettuce or endives undergo a similar process: the bottom parts are placed in water for several days or a few weeks until there is new growth and they can be moved to soil.

Scrap Dyes

We’ve saved the most exciting use for last: dyes! Many fruit and vegetable skins have tannins that help dyes bond well to natural fibers like cotton, linen, wool, or silk. The most well-known dyes made from food scraps are onion skins and avocado pits and skins. Yellow onion skins make yellow and orange dyes, red onion skins create colors between light lilac and deep magenta, and avocado scraps make a pink dye.

These dyes can be made stronger with alum powder, a mordant which helps dyes adhere to fabric better, but they can be used without it as well because of the presence of tannins in these food scraps. Some natural dyes, like the brown colors from chestnut and walnut shells, are vastly improved with the use of a mordant. Pomegranate rinds make a yellow dye and the leaves from loquat trees make a pink dye, both of which work best using a mordant.

Scraps in the Big Picture

Sometimes the scraps from your food just can’t be eaten or used, and that’s okay! When you get to this point, what’s most important is diverting your food waste from the landfill. If your city has a municipal composting program, you may have curbside compost pickup which is an easy way to reduce the emissions of your food waste, but you can also easily set up a compost in your own backyard, or get a small vermicomposting bin for your kitchen. Food waste can also be used to feed a biodigester, which produces biogas that you can use for energy. Both composts and biodigesters are part of our ongoing research at our production center, so you can expect an article soon about the merits and challenges of these systems in an urban setting. And lastly, if you do not have access to municipal or domestic compost where you live, you can see if any farmer’s markets or local gardens collect compost, and bring your food waste to them on a weekly basis. 

When it comes to food, there are so many systemic and cultural barriers to consuming it mindfully and avoiding waste. Overcoming preconceptions about food scraps that are seen as non-food is one part of working against these entrenched cultural beliefs that promote excessive waste. The problem, like any environmental issue, does not come down to just personal choices, but when these small changes are implemented at a wide scale, they can have significant effects, not just in the amount of food that goes to waste, but towards treating the food we have with respect. When we stop taking food for granted, we respect the seasonality of our produce, and stop letting vegetables go bad due to poor storage. You can read about these two related practices in the previous articles of our Knowing Our Food trilogy, and learn about how to preserve food for long or short periods.

The post Knowing Our Food: Scraps first appeared on Critical Concrete.

Though food nourishes us every day, there is still much that we can learn about it. At Critical Concrete, we aim to consume as much local, seasonal food as possible and we have recently started growing it ourselves in our food forest. Unfortunately, it is quite common that we as a society eat food without paying attention to its seasonal availability; it is easy to be influenced by a globalized system that makes practically any food available at any time in the year regardless of climate and the environmental impact. The production of food outside of its peak season can have 3-10 times the emissions as food imported from better climates, so it is important to not only support local farmers, but also to mind the seasonality of fruits and vegetables.[1] While some imported foods, such as almonds and avocados, are imported by boat and have a lower footprint than locally produced options, other more perishable foods are freighted by air, which creates 50 times the carbon emissions as boat transportation.[2] Aside from environmental friendliness, seasonal, local food can be more nutritious and flavorful as it has more time to ripen before harvest, and supports small farms and sustainable farming practices.

That being said, choosing local and seasonal produce means nothing if our food goes bad before we have the chance to eat it. That means that storing food to extend its lifespan is highly important. This research grew out of our curiosity to know more about alternative ways of storing food that are not energy consuming. However, as we encountered more information, the research evolved to focus more on food knowledge, with the aim of informing ourselves and our readers about the needs of our fruits and vegetables and how we can store and consume them. Our upcoming articles from this research will delve into the topics long-term storage, food production, and the use of food scraps, and in this article, we will discuss how to make use of conventional kitchen storage to keep food fresh. 

Food Waste and the Fridge

Food waste is an immense problem that worsens each year. In fact, fighting food waste has been determined to be one of the most urgent solutions to fighting climate change.[3] The production and disposal of wasted food results in water waste, land waste and deforestation, and greenhouse gas emissions. Although a tremendous amount of food waste is the result of industrial food practices, in Europe 42% of food is thrown out by the consumer, and only one third of that food wasted consists of inedible residuals (skin, shells, peels).[4] Regardless of whether climate change can be tackled through individual actions, consumers can still reduce the amount of food lost to spoilage in their own homes. Even if it does not solve environmental issues in and of itself, when we learn about proper food storage and reduce our waste, we save money and take the first steps toward better societal food practices.

At first we were inclined to look for alternatives to our usual house appliances like the fridges, as refrigerants like chlorofluorocarbons (CFCs) are the main cause of the depletion of the ozone layer.[5] This led us to a few methods of long-term storage, which we built as prototypes to evaluate their efficacy in the climate our research lab is located in. Keep an eye out for our next article, detailing these methods and their benefits for different foods and environments.

However, it can’t be ignored that storing food in the fridge and freezer is such common practice, so this article will describe the ways to reduce food waste in the context of conventional storage practices. Thus we first have to analyse the way the fridge is used, to know its strong and weak points and the way it works. Additionally, it is crucial to understand the process of food decay and the science behind it. Once it is understood how food decays, the same principles can be applied everywhere. In order to reach a balance in the system, minimizing waste and prolonging the life of food, we must first know the needs of fruits and vegetables and demystify their storage environments, both artificial and natural.

Where to store different fruits and vegetables

Food Decay

Knowledge about everyday storage of fruits and vegetables is essential. In order to better understand the proper storage of fresh vegetables and fruits, the first step is to clarify the biochemical characteristics and processes which occur after harvesting. This knowledge can help reveal why certain foods become rotten very fast whereas other foods last for a long time. This phenomenon is influenced by two factors: the speed of natural metabolism depending on the specific plant and the way it is stored. 

Enzymes are proteins which serve as catalysts to chemical changes in living organisms and there are thousands of different enzymes with varying functions. Enzymes in our food cause changes to fruit and vegetables which cause them to spoil. In cool temperatures, these enzymes slow their activity, and they can die when cooked above 60 degrees.[6] 

Aside from enzymes, three other rotting agents can reduce the life of food. These are mold, which is visible, yeasts, which convert sugars into alcohol through fermentation, and bacteria, some of which can poison food.[7] Using this information, we can determine how to avoid mold and bacteria, and slow down the process of decay.

Conditions for storage

The best storage method for a given food depends primarily on three parameters: temperature, humidity and ripening.

Temperature: Cooling down slows down the metabolic process and thus has an immense effect on preservation. Nevertheless, there are certain plants, such as bananas, tomatoes, eggplants or cucumber which are very sensitive to the cold and also others which lose vitamins and taste.[8] Moreover you should take into consideration where in the refrigerator to put things. The middle and the back are usually colder than the other areas of the fridge.[9] As there is no cooling on the bottom cold air coming from the middle can warm up and rise up which leads to the different temperatures levels.[10] 

Zones of the fridge and their temperatures

Humidity: Many fruits and vegetables, such as cucumbers, leafy greens, carrots and roots, are susceptible to humidity loss and shriveling.[11] For these, it is important to ensure a high level of atmospheric humidity. Many refrigerators have a crisper drawer for vegetables in order to keep a higher level of humidity. Some vegetables that should definitely be stored in the crisper drawer are spring onions, celery root, spinach, and leeks.[12] Otherwise, vegetables that are susceptible to moisture loss can be wrapped in damp towels and stored in other areas of the fridge.

Ripening: In basic terms, ripening can divide produce into two groups: the kind that continues the process of ripening after the harvest and the kind which abruptly stop ripening when harvested. This fact depends on the natural plant hormone ethylene. Ethylene is a gaseous hydrocarbon (C₂H₄) which speeds up the ripening process.[13] Some fruits and vegetables release ethylene gas in the process of becoming ripe.[14] Others, by contrast, are sensitive to ethylene and absorb it.[15] If you do not want to speed up the ripening and  spoiling effect, try to store ethylene-sensitive vegetables apart from those which release a lot of ethylene. 

Ethylene production and sensitivity in fruits and vegetables

According to their ethylene production, apples, tomatoes, peaches, apricots, avocados, kiwi, mango and bananas should be stored apart from other fruits and vegetables.[16] But you can also make use of this property when you want something to ripen faster. In that case, you purposefully store high ethylene producers together with ethylene sensitive ones.[17] When you have green tomatoes you can store them together with apples in order to get them to ripen faster.      

Referring to proper storage, there are some rules of thumb about food that should never be stored in the refrigerator. Fruits sensitive to cold are pineapples, avocados, bananas, mandarins, mango and melons.[18] Vegetables sensitive to cold are artichokes, tomatoes, potatoes, eggplants, garlic and onions.[19] Nevertheless, there are some real divas who cannot really decide whether they want to be stored in the fridge or in the room. Cucumbers and zucchinis for example are sensitive to cold but if too warm they lose humidity and start to shrivel fast.[19] Therefore, they should be stored in the crisper drawer or in the top part of the refrigerator, wrapped in a damp towel to avoid cold damage and humidity loss.[20]        

Additional Specific Storage Strategies 

With this knowledge of general food storage, we can delve into more specific ways to increase the lifespan of our fruits and vegetables. Berries and cherries are susceptible to mold, so they should not be washed until just before they are eaten.[21] Also, berries are often quite fragile and should be stored in a single layer, if possible.[22] Figs are sensitive to humidity, which makes paper bags good storage containers to absorb their excess moisture, but they can also be stored on plates in the fridge.[23]

As for vegetables, removing rubber bands from the stems is always the first step.[24] Radishes, beets, carrots, and turnips, should be separated from their greens to avoid losing moisture in the roots.[25] Then, the roots can be stored in an open container with a wet towel placed on top.[26] Greens are best in closed containers alongside a damp cloth to keep them from drying.[27] However, you can save room in the fridge by storing kale, chard, and collard greens upright in glasses of water on the counter.[28] Celery and fennel can be stored this way as well.[29] Asparagus is best stored upright in a water inside the fridge.[30] It should be noted that using paper bags, reusable containers, glasses, or damp cloths should make it easy to eliminate the need for any single-use plastic inside the fridge.

Conclusion      

Hopefully, being more cognisant of the needs of fruits and vegetables can limit food ending up in the trash or compost. Now that we understand how the chemical processes happening inside fruits and vegetables cause them to react to different conditions, we can store it in the right way. We can take advantage of the different areas inside your fridge, and organize our fridges to maximize the lifespan of our food. To help adjust to all this new information, we produced a chart to help understand fruits and vegetables and store them in the best way possible. Download it, print it, and put it on the wall in your kitchen! 

In our next article about food we will discuss different ways to store food for longer periods of time and the benefits of each method. Stay tuned to learn how fruits and vegetables can be enjoyed past the periods when they are in season, without forfeiting the nutritional value and flavor of eating seasonal food.

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Bibliography:

[1] https://ourworldindata.org/food-choice-vs-eating-local, opened 8.12.2020.

[2] Ibid.

[3] Hawken, Paul. Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming. New York, New York: Penguin Books, 2017.

[4] Principato, Ludovica. Food Waste at Consumer Level a Comprehensive Literature Review. Springer International Publishing, 2018. p. 5.

[5] https://www.conserve-energy-future.com/causes-and-effects-of-ozone-hole.php, opened 8th of December, 2020.

[6] Seymour, John. The Self-Sufficient Gardener: A Complete Guide to Growing and Preserving All Your Own Food. Dolphin Books, 1980. 

[7] Ibid.

[8] https://www.rollende-gemuesekiste.de/wp-content/uploads/Lagertipps.pdf, opened 24.11.2020.

[9] Ibid.

[10] Ibid.

[11] 

[12]https://myplasticfreelife.com/wp-content/uploads/images/Berkeley%20Farmers%20Market%20Tips%20for%20Storing%20Produce.pdf, opened 27.11.2020.

[13] https://www.theproducenerd.com/2018/02/what-is-ethylene-how-is-it-used/, opened 10.12.2020 December

[14] Ibid.

[15] Ibid.

[16] Sächsische Landesanstalt für Landwirtschaft. Verbraucherinformationen Obst Und Gemüse Richtig Lagern, 2003.

[17] https://www.rollende-gemuesekiste.de/wp-content/uploads/Lagertipps.pdf 

[18]https://myplasticfreelife.com/wp-content/uploads/images/Berkeley%20Farmers%20Market%20Tips%20for%20Storing%20Produce.pdf, opened 27.11.2020.

[19] Ibid.

[20] Ibid.

[21] Ibid.

[22] Ibid.

[23] Ibid.

[24] Ibid.

[25] Ibid.

[26] Ibid.

[27] Ibid.

[29] Ibid.

[30] Ibid.

The post Knowing Our Food: Storage first appeared on Critical Concrete.
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Concrete, as the most used building material worldwide has a huge impact on our cities, societies and environment. Much of our research is based on the idea to create an alternative solution for conventional methods of building, such as building with concrete. In this article, we will tackle basic and relevant knowledge and information about concrete, to understand why it is important to think about alternative solutions for the future of our building habits. This write-up will be part of a series of small papers related to meaningful knowledge, to understand why it’s urgent to rethink our conventional building approaches.

Concrete, cement & mortar – definitions

To give a brief overview of what we are talking about in specific, we will first define the most important terminologies that we will need to understand the whole topic around concrete.
Four important terms you should know about and understand their exact definitions: 

Typical composition of concrete

cement  // səˈment

Cement is the key ingredient to mix concrete. This product is mainly made out of crushed limestone mixed with shales and slates, shredded to a fine powder and heated up to approximately 1450°C. The heat causes a chemical reaction, also known as calcination.[1] That reaction along with the heating process causes a high amount of carbon-dioxide emissions, which makes cement production a big driver of greenhouse gas emissions. The entire process happens in a giant mixer, called a cement kiln. [2] The most popular kind of cement is portland cement, developed in England in the early 19th century. [3]

concrete // ˈkänˌkrēt

Concrete is an artificial building material, which consists of a binding agent like cement or lime, in addition to water and aggregates (sand and gravel) as well as potential  additives (like fly ash or plasticizers). The cementitious part gets liquified with water. By adding water to the cement a chemical reaction is caused and the process of crystallization begins. In the next step some additives such as gravel and sand are added. These aggregates are held together by the liquified cement. Once the whole mixture is cured, this process will finish with a solidified product, called concrete.

mortar // ˈmôrdər

Mortar is a workable paste, used to bind bricks, stones or to fill gaps and holes. The basis is made out of a binding agent (such as slaked lime, ash or, most commonly nowadays, cement) added with water and a fine aggregate, mainly sand. 

Mortar is one of the oldest building materials, used for many thousand years. For a long time, slaked lime, volcanic ashes or clay worked as a binding agent. During the nineteenth century portland cement was invented. From that time cementitious mortar rose in popularity and replaced the old binding products.

These two kinds of mortar differ in two ways. On the one hand cementitious mortars usually are more workable due to faster curing, higher water resistance and less cracking, on the other hand non-cementitious mortars significantly cut greenhouse emissions while processing. It even can absorb CO2, which appears to happen when lime mortar cracks, so that air (especially CO2) can be absorbed. By absorbing CO2, lime mortar is even molding and gets even stronger.[4] To put it plainly:  it’s an environmentally friendly and more sustainable alternative.

reinforced concrete // ˈˌrēinˈfôrst ˈkänˌkrēt

In most cases concrete is combined with steel rebars, to compensate for the low tensile strength. The capability of concrete to react on compressive load is ten times bigger than the capability to bear tension loads.[5]

A more advanced and further developed version of conventionally reinforced concrete is prestressed concrete. To make concrete structures more durable against tensile forces, tendons, a high performing kind of rebar gets tensioned. Mainly these tendons are wires or threaded rebars. When applying in the casted concrete, the concrete part gets compressed, which gives the structure a higher performance, while being in service. [6]

Why is cement concrete so popular?

There are many reasons for its popularity: its liquid stone characteristics were revolutionary and created the possibility to make nearly every form out of concrete.

Cement concrete structures can be segmented and precast, making it suitable for big construction projects; and once solidified, it is a very strong material with the ability to bear high amounts of load. Designers adopted the versatile material, and nowadays we find furniture and accessories made of this material, in every kind of shape.

The use of concrete can be dated back to the ancient times. Romans mastered the use of hydraulic lime as a binding agent, called “opus caementicium”. After the fall of the Roman empire, the use of concrete faded, till it got resurrected in the early 19th century. Instead of using hydraulic lime, portland cement, a further development of the ancient version, was invented and led to a big rise in popularity of concrete in building industries. The first buildings during this time were bridges, foundations and harbours, facilitated by the compressive strength and workability of the new material.[7] 

In the late 19th century iron rods, and later steel rebars, were added to poured concrete to increase tensile strength. It was mainly developed by the French Joseph Monier [8]  – an invention which is ubiquitous in building industries nowadays. This invention led to a big rise in popularity in the residential and social housing sector. In comparison to conventional houses in those days, new concrete based housing projects were more durable, termite and fire resistant. The workability of concrete made it fast and easy to use on site. Pre-castable and serial development of construction elements cut costs significantly. In the 50s of the last century, concrete played a major role in evolving the architectural style of Brutalism, a socio-aesthetically driven architecture movement of showing raw, honest constructions often used for big scale civic and public projects. This architectural style was a dominating force during the next two decades. [9]

In addition, the raw materials of concrete are available in large quantities around the globe, which makes concrete cheap to produce. Limestone, sand and gravel are quite cheap. The main processing costs are caused by the cement production. 

What quantity of resources are needed to produce cement concrete?

There are four main components of cement concrete (cement, water, sand and gravel). For reinforced concrete, there is an additional component – steel. Besides these materials, there are more raw resources needed to produce the main ingredients. To produce one tonne of cement, approximately two tonnes of raw limestone are necessary. [10] The production of cement is a high energy consuming process. One ton of cement takes about 120 kWh of energy in process heating. This energy is mainly obtained from fossil fuels and burning waste. [11]

The cement concrete recipe

There are several different recipes for making concrete. The recipes mainly differ in the ratio of cement and the added aggregates. Concrete can be mixed with different ratios to get a higher load bearing capacity or to get a higher ability to withstand different exposures, such as seawater, moisture or frost.

The following recipes just give you a basic overview about how a classic mixture of concrete could look like:
A standard concrete mix consists of 1 part water (7,7%), 2 parts cement (15,4%) , 4 parts sand (30,7%) and 6 parts gravel (46,1%). [12] 

The higher the load the more cement you’ll need (f.e. a concrete column, foundation needs 1 part water (11,1%), 2 parts cement (22,2%), 2 parts sand (22,2%) and 4 parts gravel (44,4%) ).
Around 70% of the built concrete constructions are reinforced with steel, so you would usually have to add a certain percentage of steel rebars to the produced concrete (60-80 kg/m3 of concrete).[13]

That means a ton of average concrete consists of:

77 kg of water (7,7%)154 kg of cement (15,4%)307 kg of sand (30,7%)461 kg of gravel (46,1%)

Components of 1 tonne of concrete

Where is concrete used?

The use of cement concrete has various fields of application in construction and design. Since it was developed in the early XIXth century as a powerful structural material, it can be found in several constructive elements. The constructive elements made out of concrete can be summed up in three main categories:

massive built horizontal and vertical load bearing elements such as foundations and walls, used for small to middle scale buildings, such as residential housing.filigree skeleton construction elements, such as pillars and beams, mainly found in high rise buildings and large scale commercial buildingsspecial construction elements for infrastructural and exceptional building typologies, such as bridges, tunnels, dams or bunkers.

Where is concrete useful?

Nowadays concrete is used in many different ways. All constructive elements can be made in concrete and in most cases they are realized with this material.
But is it really necessary to replace other common construction methods with concrete?
It makes sense to use concrete in constructions, where load bearing elements have to bear big compressive strengths. A high rise a few hundred meters high? A tunnel? A dam? For sure! – There are fields of application, where no other material performs as well as concrete but in many cases concrete is used in small scale projects, where it is unnecessary and over proportioned.

How sustainable is cement concrete?

Concrete is certainly one of the building materials which gives a nearly unlimited range of use. As mentioned before, there are many upsides to using concrete. But there are always two sides of the coin.

A general definition for sustainability is meeting the needs of the present without compromising the ability of future generations to meet their needs. Sustainability is often discussed in environmental terms. It can also be related to two other important topics: society and economy.

Obvious and hidden impacts on our environment

Pie chart comparison between countries CO2 emissions and cement production

The impact on our environment caused by the cement industry and by building with concrete is enormous. The production of cement is a high energy consuming process. This energy is mainly obtained from fossil fuels or burning waste [14] In addition the chemical process of producing cement releases one molecule of carbon-dioxide per each molecule of calcium silicate hydrate. For each ton of produced cement, one ton of CO2 is emitted just by chemically processing it [15] Besides the vast amount of carbon dioxide emitted, many other hazardous air pollutants such as NOX or PM10 are emitted during the process. [16]

Cement is just one part of concrete. The added aggregates, such as gravel and sand, are mined in humongous amounts to cover the demand of concrete industries. Many environmental systems are suffering from negative effects such as land loss by erosion, destruction of natural habitats, sealing and contamination of soil. Some of these aggregates, especially sand, have to be shipped around the world to service demands. [17] Just to give a short glimpse of one of the biggest cruxes in world of the concrete industries – new developing middle-east states, such as the United Arab Emirates or Qatar have to import big amounts of sand to service their huge demand in building industries, despite the fact that cities like Dubai or Qatar are located in the middle of sandy deserts. [18] However, not all of the sand we can find on the globe is suitable for concrete production; desert sand is too fine and round to be used as an aggregate. [19]
Furthermore, concrete production is a thirsty industry. It needs almost 10% of annual industrial water withdrawal, and 75% of the concrete production takes place in regions which are already facing water stress and drought. [20]

Beside this, the impact on society has to be emphasized. The internationalization of architecture and modern building technologies have a negative influence on vernacular building technologies and local architecture. New buildings tend to be built in a modern way with modern materials, such as concrete. Cost efficiency, the establishment of new building technologies and the time aspect are reasons for a significant decrease of traditionally built projects. 

Impact of globalization and industrialisation on building traditions.

Comparison between the use of concrete and other building materials

One of the main issues caused by that situation is the loss of building knowledge and traditions. Traditional building techniques are being replaced by modern approaches. Around the world, houses and cities have been built according to local tradition for centuries. Now, knowledge that was gained in a long and enduring process is about to get lost in a few decades. 

Main drivers for the loss of vernacular architecture are caused by the growing globalization and industrialization of the world. Innovations in building technologies can be spread easily around a fully connected world. Rare materials not locally available can be easily shipped from anywhere – and they get transferred in humongous amounts around the planet. 

Downcycling cement concrete

The economic sustainability of concrete is always mentioned as a big pro. Nonetheless there are a few facts which are not properly taken into consideration. The production of concrete is cheap in comparison to other materials. A main reason for this, is that the aggregates you need to mix concrete are available in large quantities almost everywhere around the planet. But in recent times the local availability of certain components, such as sand are diminishing. [21] Our resources on the planet are finite, so using and monetizing resources as if they are infinite is unsustainable. To address this, the concrete industry tries to emphasize their product as recyclable, but to make it clear – concrete is not recyclableRecycling means, returning a material into a previous stage of a cyclic process. In case of the mentioned material, this is not completely possible. During calcination, the processing of the raw resource of limestone comes to a point of no return. Once cement is made, the process is irreversible. There is no commercially viable process to recycle it.[22] Recent reusing methods of concrete consist of shredding it and mainly using it as gritting material for infrastructural projects. In some cases this crushed concrete can be used as an aggregate to partly substitute gravel in concrete. Nevertheless these substitutes are small in numbers and in the end new concrete still requires additional water, cement, sand and gravel [23] Technically, the recent approaches to recycling concrete can be better named downcycling processes or a kind of mitigation. Many experts criticize the bigger potential of reusing shredded concrete for new concrete projects, [24] an effort which should be broadened in the future. 

Contradictive durability of concrete structures

Many proponents often mention concretes’ durability as a big pro. The use of concrete without adding any other materials (such as rebars, made out of metal) technically creates a very durable building material. Despite, most of the applied concrete is reinforced to be able to react on tensile stress. But the application of reinforced concrete in terms of durability is a contradiction in terms. Here nature inevitably can shorten the life span of buildings built out of reinforced concrete. Due to different thermal expansions and the inevitable inheritation of oxidation of the used steel rebars, concrete constructions suffer fast deterioration during their lifespan. Recent studies have shown that there is a 50% chance of reinforced concrete structures to not fulfill their service in terms of load bearing after just 35 years of use. [25]

What can be used instead of cement based concrete?

Concrete as a kind of fluid stone has found use in all fields of construction. But is it always necessary to use concrete? There are new materials and also tried and trusted methods of building which have mostly been replaced by concrete solutions. The replacement of conventional portland cement based concrete can cut greenhouse gas emissions and other environmental impacts significantly. Basically there are two main ways to avoid a humongous use of classic portland cement based concrete. The first one is to substitute or avoid the most polluting ingredient of classic concrete, portland cement. In a second scenario different building approaches with alternating materials or other building techniques can be applied.

Cement substitutes

First of all, portland cement based concrete mostly can be substituted by pulverized fly ash (PFA), which is a side product of coal burning processes. Another substitute with a big potential is Ground Granulated Blast-furnace Slag (GGBS), which is able to replace portland cement up to 90%. GGBS substituted concrete sets more slowly than concrete made with ordinary portland cement. The higher the amount of GGBS in the cement mix the longer it takes to cure. Besides this, a positive side effect of using GGBS substituted concrete is that it continues to gain strength over a longer period leading to improved overall durability and life expectancy. [26] Nevertheless the mentioned substitutes are by-products of other industries, such as coal, steel or aluminium production, which also have an enormous negative impact on our environment.

Green concrete

During the last decade several scientists started working on green alternatives for concrete. The most advanced approaches use micro organisms such as algae, bacteria or fungi for biocement production (CaCO3) by using the metabolic activity of these microorganisms. [27,28] Some of these bioproducts achieve similar specifics as classic portland cement and present a feasible and viable alternative to conventional portland cement based concrete.

lternative construction methods

Besides an ingredient-related replacement of conventional concrete, there are many tried and trusted construction methods which were applied in vernacular building styles and local architecture traditions. There is no convincing evidence that justifies concrete as the ultimate building material for most building tasks.

This table aims to present a series of more ecologically friendly solutions for common uses of cement concrete:

construction elementclassic building material
to be replaced / substitutedeco friendly alternative (not exhaustive)foundationsreinforced concretetyre foundation (for point foundations) [29]
gabion foundations [30]pillarsreinforced concrete
steelwooden constructions (bamboo, pine, GLT – glue laminated timber)
cardboard tubeswalls(reinforced) concrete
bricks
steel sandwich panelswooden constructions (CLT – cross laminated timber, framework constructions)
rammed earth (clay)
hempcrete
bricksflooringcement based screedclay 
wooden planks roofsreinforced concrete (flat roofs)
steel sandwich panelswooden constructions
thatched roofs
green roofs
hempcretepathingcement based pavement
asphaltnatural stone :
cobblestone, granite plastergypsum based plaster
cement based plastercardboard + lime plaster [31]
hempcrete plaster
straw clay based plaster

Conclusion

Concrete plays a major role in building industries. The further development of newly industrializing economies with huge demands on concrete are driving the ongoing trend of a growing concrete industry. Beside its advantages and big popularity, concrete brings a lot of negative impacts on global warming, environmental systems, building culture and social city development. It is important to mention that concrete lacks recyclability. The present system around the concrete industry can be summed up as a cradle-to-grave system. Resources are extracted, used and then wasted and dumped or downcycled in the best case scenario. Due to the chemical process, cement, the most important ingredient of conventional concrete, will never be recyclable, which underlines the unsustainability of a whole industry. Its fast and wide availability and low costs in production make it popular for many large scale projects. 

Nevertheless there are recent approaches to develop more sustainable alternatives to the classic portland cement-based concrete by trying to avoid or minimize the use of cementitious components, aiming for a better reusability and recyclability of resources. 

In addition, investigating forgotten vernacular solutions reopens fields of research to move forward to a more environmentally respectful architecture. Stay tuned on our continuous research, on social media and if you can and feel like supporting the initiative, make a small donation on our Patreon! 

Sources

[1] https://www.sciencedirect.com/science/article/pii/B978008034720250023X , opened 12.08.2020

[2] https://www.britannica.com/technology/cement-building-material/Extraction-and-processing , opened 12.08.2020

[3] https://www.screedscientist.com/portland-cement-a-brief-history/ , opened 18.08.2020

[4]  Quantitative Analysis of CO2 Uptake and Mechanical … – MDPIwww.mdpi.com › pdf , opened 23.09.2020

[5] https://diglib.tugraz.at/download.php?id=576a7195cc9f9&location=browse , opened 11.08.2020

[6] 372R-13 Guide to Design and Construction of Circular Wire-and-Strand-Wrapped Prestressed Concrete Structures , 2013

[7] Historic Concrete in Scotland Part 1: history and Developmentpub-prod-sdk.azurewebsites.net › api , opened 13.08.2020

[8] https://www.britannica.com/biography/Joseph-Monier , opened 13.08.2020

[9] https://www.architectureanddesign.com.au/features/list/a-look-at-brutalist-architecture , opened 20.08.2020

[10] http://ecosmartconcrete.com/?page_id=208 , opened 12.08.2020

[11] https://global-recycling.info/pdf/GLOBAL-RECYCLING_2-2019 , opened 11.08.2020

[12] https://www.marshalls.co.uk/gardens-and-driveways/blog/how-to-mix-cement-to-make-mortar-or-concrete

[13] https://diglib.tugraz.at/download.php?id=576a7195cc9f9&location=browse , opened 26.07.2020

[14] https://global-recycling.info/pdf/GLOBAL-RECYCLING_2-2019 , opened 11.08.2020

[15] http://ecosmartconcrete.com/?page_id=208 , opened 12.08.2020

[16] http://ecosmartconcrete.com/?page_id=208 , opened 13.08.2020[1] http://ecosmartconcrete.com/?page_id=208 , opened 13.08.2020

[17] https://www.globalconstructionreview.com/news/shifting-sands-concrete-hungry-singapore-orders-mi/ , opened 28.07.2020

[18] https://www.bbc.com/worklife/article/20160502-even-desert-city-dubai-imports-its-sand-this-is-why , opened 19.08.2020

[19] https://www.bbc.com/worklife/article/20160502-even-desert-city-dubai-imports-its-sand-this-is-why , opened 19.08.2020

[20] https://www.nature.com/articles/s41893-017-0009-5.epdf , opened 26.07.2020

[21] https://www.globalconstructionreview.com/news/shifting-sands-concrete-hungry-singapore-orders-mi/ , opened 29.07.2020

[22] CSI-RecyclingConcrete-FullReport.pdf , opened 29.07.2020

[23] https://www.archdaily.com/933616/is-it-possible-to-recycle-concrete, opened 30.07.2020

[24] https://eu-recycling.com/Archive/22163 , opened 30.07.2020

[25] https://www.structuremag.org/?p=9459 , opened 18.08.2020

[26] https://www.greenspec.co.uk/building-design/concrete-cement-substitutes/ , opened 25.08.2020

[27] https://www.mdpi.com/2071-1050/10/11/4079#abstract , opened 25.08.2020

[28] https://www.sciencedirect.com/science/article/pii/S2215017X18302923 , opened 25.08.2020

[29] https://criticalconcrete.com/tyre-foundations/ , opened 25.08.2020

[30] http://bristolgreenhouse.co.uk/site/foundations.html , opened 25.08.2020

[31] https://criticalconcrete.com/out-of-the-box-vol-3/ , opened 25.08.2020

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In the former articles was explained some of the advantages to be found within these ancient  common methods of charring wood. Historically and within many cultures, there are a myriad of charring modalities. In this article you will find adapted and illustrate one of those methods using a small wood burning flash oven that can effectively provide the charring levels needed without overtly case timber that has been dried too rapidly. This leads to reversed stresses; compression stresses on the shell and tension stresses in the core. This results in unrelieved stress called case hardening.[1]) the wood items placed through it. In this article we explain how our charring station is built and how it works. Charring systems like this one have been commonly found in many cultures and this is an adapted version of several of those [2]. It is adaptable, is easy to operate and runs without the use of gas or special tools. All that is needed are some (fire) bricks and scrap wood for fuel.

Counter-intuitively, charring wood has several astonishing advantages without involving any chemicals or additional energy consumption. The idea is to sear the surface of the wood without combusting the whole piece nor damaging the interstitial aspects of the wood so it will not warp over time. Besides giving the material an interesting and unique look, the process leads to a triple protection, all without the need of repeating the process after some time has past:

fire protection – charring the surface starts a superficial carbonation of the material and thus lowers the thermal conductivity. termite and mold protection – charring wood destroys the wood’s nutritional value to insects and fungi.water protection – the enhanced carbonation gives the charred layer a waterproof resistance, as water slips on burned wood like over an oily surface.

The easiest and most popular way to char wood commonly found today is probably with a blow torch. This can work, but regrettably too often performed without the attention to detail not to stress the wood from within. It’s easy and practical,  especially for small or irregular pieces but has to be performed with caution. But when searing many big wooden pieces it is slow and uses a lot of gas. These searing modalities are not to be confused with traditional Japanese, 焼杉 (Yakisugi) which is often misrepresented as 焼き杉 (aka shou-sugi-ban”) [3] – us included, in our previous articles!.

Yakisugi can only be achieved with a limited range of Cypress species found on the islands of Japan[4] and is a very unique process found within several methods of crafting guilds. The most commonly seen being where three planks of wood get bound together to form a long triangle and a fire is started in the resulting tube. There are several other methods, but they are for very specific formats and within context to only yakisugi and not the charing modalities found within other cultures.This technique works well only when you have similar boards, as it’s complicated to set up when boards have different widths and lengths.

Terunobu Fujimori, Tea House, Barbican. Photo Ben Tynegate

The birth of the charring station

This contemporary oven is based on some of the principles of a rocket stove. The main idea is to create a fire within a brick tube, which will become very concentrated and strong due to the tube-generated draft-effect (for more explanation on this and general information, check our articles on rocket stoves). Just over the burning material, where the fire is very strong, there will be small slots on the opposing sides of the tunnel. The wood, which needs to be seared, can be passed easily through the fire and thus be charred fast and safely.

After this oven was created with commonly available materials which enables us to char planks and boards of different sizes in an effective manner. This oven also allows the operator safety by lowering the risk of burning their hands, while also providing more control of searing the wood and less waste of fuels which is then more environmentally friendly.

How does the charring station work

Author: Melana Jäckels

1 – The main part is a L-shaped tunnel. On the bottom it has an opening on the side, where the air goes in and it flows all the way through the tunnel up to the upper opening.

2 – Right after the curve, the fireplace is based on a second layer. Its bottom has two small gaps for the air to pass and to allow the finer ash to fall.

3 – It is important to have a tunnel that is at least 5 cm wider than the boards you plan to char. If a board fills the whole wide of the tunnel it stops the draft and decreases the fire.

4 – On the same level as the fire is also the stair-like firewood intake. The fire is started and fed from here. It’s important to have a brick to close the firewood intake so it does not disturb the air draft in the moments no wood is inserted.

5 – In the chimney, right above the fire, there are two vertical slots on opposing sides to insert the wood you want to char.

6 – Above the inserting slots the chimney narrows slowly. This is important to not happen in a sudden step, as it otherwise will decrease the draft and create a lot of smoke coming out of every small gap.

Building your own charring station

For our charring station we used 12 big bricks (ca. 29x18x9), around 70 medium-sized, red bricks (ca. 23x10x7) and 5 fireproof bricks (22x10x2). Depending on what is available, numbers and materials might be adjusted. Before starting the building process, it is important to choose a big outside space, which is not too windy and has a relatively leveled ground, with enough space on each side of the station to pass the board through.

Step by step:

First, we made a fire-resistant base which is leveled and flat. For this we used the big bricks

Afterwards we started to build a tunnel for the air intake with dimensions of 90 to 25cm. It is important that it is stable and possible to close with removable bricks on the sides

We covered the tunnel with the red bricks and left two gaps of about 1,5 cm each as seen in the picture.

The fireplace gets covered with fireproof bricks and the next line of bricks is put on all sides

To protect the walls, we also placed fireproof bricks around the fireplace

The next step is to build the J-shaped intake with steps made of bricks, towards the fireplace. It is important to make sure its height will match up with the next row of bricks

Now it is time to create the slots where the to be charred boards will be inserted. For that we put two bricks flat across from each other. This  station works  well for boards with a maximum width of 16 cm. If you plan to use a roller stand, make sure the height of your slots measured from the ground is adapted to the height of the roller stand)

Above the slots we continued building the chimney in the original diameter for a few more rows, but then we start to become narrower by changing the order of the bricks

In this timelapse video you can see how we built up the station in 10 seconds!

How to use the Charring Station

Before starting, make sure to have the right equipment (fire resistant gloves, a mask, a bucket of water / sand, and a fire extinguisher) and enough material to burn! If you want to char a big quantity of wood it is also quite handy to have rolling stands.

Starting the fire works best when you build a little teepee out of dry kidlings and put some sawdust on it, light up the tip of a rolled paper (A4 is enough), and move it slowly into the directions of the teepee. Besides you can put another burning paper over the chimney, to facilitate the draft-effect.

To avoid unnecessary interruptions, it is important to have a constant refilling of firewood. As soon as the fire burns strongly, the opening of the firewood intake can be closed and the boards can be inserted through the slots. Inside, the strong and concentrated fire will char the surface of the wood from below and the sides. The boards should be pushed through the fire in small steps to have a satisfying and regular result. After the first part of a board is charred, it can be taken out and pushed upturned through the fire again until both sides are completely charred. If the results are not satisfying, the pace should be adapted. Depending on the size, form and species of the wood it will take its respective time to finish one piece.

Once the board is charred it should be brushed with a metal brush and oiled. As the charring process dries the wood very rapidly, depending on its nature it might have a tendency to crack. The linseed oil will nurture the wood and compensate for this effect. For more information on this see our article on Natural Wood Protection.

Conclusion

We are using this method for a while now and we are super satisfied with the results. Not only we save time but also we are more independent of gas. The work with the charring station is safe and convenient. The station is easily adaptable and can be modified to different dimensions. We are looking forward to using the station in the future and improving it further.

Check our YouTube video for a step-by-step tutorial how to build up your own station!

We would like to sincerely thank Jay C. White Cloud for his time, valuable input and collaboration on this research.

Sources

[1] Wikipedia “Wood drying”, [Online] available at https://en.wikipedia.org/wiki/Wood_drying (Last accessed in July 2020)

[2] Jay C. White Cloud [Tosa Tomo Designs] https://about.me/tosatomo

[3] [4] Nakomoforestry “Yakisugi” Or “Shou Sugi Ban”? Learn What You Should Call It, And Why”, [Online] available at https://nakamotoforestry.com/yakisugi-or-shou-sugi-ban-learn-what-you-should-call-it-and-why (Last accessed in July 2020)

Picture: Terunobu Fujimori, Tea House, Barbican. Photo Ben Tynegate [Online] available at https://www.ben-tynegate.com/tea-house (Last accessed in July 2020)

The post Charring Station first appeared on Critical Concrete.
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Agriculture nowadays is one of the most harmful industries in the world. It is estimated that around one quarter of the world’s emissions is coming from this sector (1). If we were able to transform today’s techniques into a mindset and strategy that rather than exploiting the environment even has a positive impact on nature, we would be able to start regenerative processes on a big scale. 

“We have disconnected ourselves from life on the planet, thinking that we are the intelligent ones.
But can’t see that we are just part of an intelligent system.”
from Ernst Götsch

Food…what?

A food forest, also called an edible forest garden, is a cultivation method that is inspired by a natural forest system and inhabits a large number of plants, ranging from vegetables and berry bushes to big fruit trees. Food forests benefit from the symbiotic interplay of the different plants and thus offer a large variety of crops without the need for intensive maintenance.

Pictures from Silver Leaf Farm, Skala, Greece
© Southern Lights Project

What is a food forest?

Conventional cultivation and gardening methods are exactly the opposite of what make the forest system work. In order to make the harvest easily accessible with large machines, only one species is cultivated in separate rows in each field. All dead organic matter is cleaned up and the missing nutrients are added through fertilizer or chemicals.

Plants disposition in a monoculture orange field
© Southern Lights Project

In a natural forest, plants automatically take up the space that is most suitable for them to receive the resources they need. Doing so, they also create or improve the habitat for other plants. The result is a deeply interwoven network of very different and complementary species benefiting from each other. Organic matter deriving from the plants and the plant’s fruit plays a crucial role in this circle. Left on the ground, it stores humidity and prevents the soil from drying out while it decomposes to nutrient-rich soil. In ideal circumstances, no human measures like additional nutrition or irrigation are required to keep this system working. The idea of ​​a food forest is not to reproduce a natural forest exactly but to have it as a guiding model for creating a resilient and productive structure that is adapted to our needs. This concept shows how the basics of the forestial system can be applied to agriculture. It mimics the main principles of a forest and consists of perennial trees and plants that provide food. They are planted in such a way that the layer they occupy in their original habitat is respected, providing the ideal conditions in regards to sunlight (2). Every operation is done in order to reach an energetic positive balance in the system, so the system regulates itself.

Pictures from Silver Leaf Farm, Skala, Greece
© Southern Lights Project

What are the impacts of a food forest?

On the one hand, a food forest rewards its creators with many advantages. Similar to natural forests, human intervention can be reduced to a minimum because the system is mainly self-regulating. With a well-designed system also the harvesting process is not necessarily more time-intensive than in monoculture. On a smaller scale, where a food forest is mainly used for self-sufficiency, the variety of products supports a healthy and balanced diet. On a larger scale, this variety of products spreads the financial risk across many types of income opportunities by breaking the dependency on one crop only. In addition, the positive impact of cultivation led by food forest principles goes far beyond personal advantages. It does not just enrich the local biodiversity of plants, but by creating a natural habitat it also increases the diversity of animals, especially insects. Farming in a food forest way can kick-start and facilitate processes to save and recreate endangered ecosystems. Furthermore, as the enriched soil, the organic matter, and the plants keep humidity and bring shade, a food forest has an enormous impact on balancing the microclimate. Thinking big, the wide-spread use of food forest principles in agriculture could lead to a considerable effect on the climate.

Lizard Eggs
Pictures from Silver Leaf Farm, Skala, Greece
© Southern Lights Project

The key principles of the food forest

Disposition of plants

The design of a food forest garden requires a long-term mindset with the attitude to look patiently into the future. In fact, the natural system takes some time to strike a balance between the species, the final forms of the plants and their proper growth. Nevertheless, it is possible to get fresh fruit and quick results from the smaller plants since the beginning of the process, as those take a short time to adapt and grow. These plants also help prepare the good soil and habits for larger plants.

A food forest garden is usually made up of layers of different plants that strategically help each other throughout their life. In good conditions, the plants themselves occupy the layer to which they naturally belong. In an agroforestry system, eight layers of plants usually have to be organized:

The Emergent layer is the tree layer that overtops the other trees, forming its crown above them. This shows us that they need maximum sunlight and do not tolerate shade. Usually, trees of this layer have only a few branches on the trunk, concentrating its growth on the crown where the sunlight is. Typical for this layer are the date palm, walnut, and pear trees. 

The Canopy Layer is composed of large fruit trees, nut trees and leguminous species with large crowns that are providing a good amount of shade during the dry and hot period. Plants are not in competition for reaching good soil, but only for capturing sunlight: trees are actually able to adapt their shape and to grow in harmony with other species to reach the best light spot. Examples for plants of this layer are mulberry, olive, fig or apricot trees.

The Understory Layer consists of small fruit trees and nut trees. Species of this layer prefer a good amount of sunlight but tolerate some shade. Examples for this layer are almond, orange, plum, nectarines, pomegranates, and apple.

The Shrubs Layer is composed of trees that need to be protected from direct sun. Plants of this layer are hazelnut, most berry shrubs and bananas.

The Herbs Layer is composed of short herbaceous plants, often annual.

The Groundcover Layer contains grasses, creepers, and low growing plants that protect topsoil from erosion and drought. This layer slows the speed of raindrops to lessen their impact and protects the soil’s dedicated network of roots, sand, organic matter, and hyphae (fungal roots).

The Vertical Layer is composed of climber plants that grow up trunks and branches of the bigger trees. 

The Roots Layer is really important because it pulls up minerals trapped in rocks to the plants: it is composed of tubers, rhizomes and bulbs.

Typical disposition of plants in a food forest system
Infographic: Critical Concrete

Thanks to the layered diversity of species, food-forest projects provide diversification of products over monoculture cultivations: each layer is in fact offering a specific variety of food in different seasons, from fruits and berries to tubers and mushrooms. In contrast to a monoculture, that requires the fixed distance between plants, agroforestry allows us to reach a much higher density of cultivation, as plants overlap in layers.

Pruning & organic matter

As mentioned before, food forests are designed to reproduce a sustainable and working forest system in which external help and additional human activities are limited, except one: pruning. “Chop and drop” is the key activity that provides the quantity of organic matter that becomes compost to fertilize the soil, extremely important to increase root activities and feed the plants. Pruning plants is also essential to help plants to breath, grow more and reach a good amount of sunlight, encouraging chlorophyll photosynthesis. The photosynthesis is pushing the mycorrhizae, a symbiotic association between a fungus and a plant, playing an important role in plant nutrition, soil biology and soil chemistry. 

Pictures from Silver Leaf Farm, Skala, Greece
© Southern Lights Project

The fertilization of the soil is constantly influenced by the production of new organic substances: the pruned branches that remained on the ground become water collectors in the rainy season and release moisture and water in dry periods. Following food forest principles is a good way to fight the soil exhaustion on a small or large scale. In fact, the use of different plants determines a symbiotic interplay in the use of the soil and is balancing nutrition resources. Every kind of soil could be defined as a “good” one: what matters is the amount of organic matter that determines the continuous fertilization of the soil. The soil is, also, acting as a sponge being a water and minerals container. Understanding of the importance of organic matter for the water management of the system can be found in the following numbers: If the amount of organic matter in the soil is increased by only 1%, an additional of 175.000 liters per hectare of water can be stored in the soil.

Comparison between an arid soil (left) and good one (right) rich of organic matter
© Southern Lights Project

Interview with Sheila from The Southern Lights Project

Food Forest had been proven a successful phenomenon on a smaller scale on a personal as well as on a commercial base. An amazing example for a prosperous sustainable business is the food forest farm The Southern Lights in Skala, Greece. Based on the organic farm of her father, Sheila introduced food forest features into her place, now cultivating more than 80 crops from which the farm and its employees can have a reliable income. 

What do I need to start a food forest?

“There is no minimum size, you can start a food forest on a spot as little as one square meter. It is helpful to have or gather some knowledge of the plants you want to put, especially their layer. And finally, you need to add a lot of organic matter..”

Are there any plants that are not so suitable for food forest?

Some plants might be not so easy to work with, like for example grains or rice and you will not get too much crop from this. But it is important to know your plants and things that might work out in some other conditions might not work out for yours.“

Should I be afraid of invasive species?

“If a species is invasive in your place, that means something is missing. Actually, those so-called “invasive” or pioneer species prepare the soil with their organic matter for other plants that have higher demands on the soil.”

Can I combine a food forest with animals?

“Animals can be very helpful for your food forest. They help to decompose the organic matter as they eat it and literally poop fertilizer. But I would rather keep my place welcoming to every species that feels comfortable in my place instead of bringing animals from outside.”

How can I know if my soil is good soil?

“Your soil should look like the soil in a forest, meaning you find a lot of organic matter on the ground, even if the very surface is dry, it is humid within deeper layers. And if you can find worms, mycelium and mushrooms it is a very good sign.”

What is the difference between “permaculture” and “food forest”?

Permaculture is a design technique, which can be applied to any kind of context. Its main ideas are Earth Care, People Care and Fair Share achieved through many principles, for example, to observe and interact or integrate rather than segregate. A food forest is a good example showing this principle being applied.”

Extract from her lecture, to see the whole presentation check our YouTube Channel

How to bring these principles to a larger scale?

A common prejudice concerning the adoption of the food forest concept to a larger scale might be the assumption that due to its unregulated structure, a forest-inspired agriculture might not be workable with large machines. But projects started and inspired by Ernst Götsch, a swiss botanist working in Brazil, had shown that large scale agriculture and the principles of a forest can go astonishingly well together.

He developed the concept of syntropic farming [Gr. syn, together with, trepein, to turn.]: usually, a minimum of 30 different species will be planted, taking into consideration their suitability to the local conditions, their ecophysiological function, their lifetime as well as the farmer’s productive goals. To make it workable with bigger machines and tools, most of the plants are cultivated in rows. In contrast to traditional farming, these rows not only consist of one single species, set apart for a few meters but follow the principles of agroforestry and food forests. These means, companion plants and trees from different layers are densely combined together to facilitate the supporting networks. Mostly fast-growing support species (like eucalyptus or mulberry) are mixed with income-generating fruit-bearing plants and trees. Natural processes are accelerated through heavy pruning of the support species in order to generate vast amounts of organic matter which will decompose to nutritious soil for the fruit trees and plants.

What all of them have in common is that the harvest is a side-effect of ecosystem regeneration, and vice versa – ecosystem regeneration is a side-effect of the efforts to produce a harvest.”
from Ernst Götsch

Bringing food forest to urban contexts

In view of the many advantages of a food forest, the question arises, how this principle could be brought into the urban context. Similar to existing gardening projects, food forests can contribute to make cities greener, bring communities together and reduce food transportation. The benefit of a food forest is that also perennial species are used. This means, once the structure of the food forest is in place, less work will be required than it may be the case with the replanting of annual vegetables. “Upgrade” existing urban gardening projects is a good start to bring the principles of a food forest into the urban environment, but also introducing it to the yards and gardens of school and kindergartens has been proven to be a good starting point so far. 

But the most practical way to bring a food forest into the city is by starting one of our own! Thanks to the introduction to the concept and the following workshop from Sheila Darmos from The Southern Lights, our very own little food forest is growing in our workshop’s backyard.

Critical Concrete Food Forest, Porto, January 2020In this video she will guide you through the planting of the different layers to set up your own edible forest.

Sources

(1) [Hannah Ritchie, Max Roser] “Environmental impacts of food production”, January 2020, online available at: http://ijsetr.org/wp-content/uploads/2017/10/IJSETR-VOL-6-ISSUE-10-1364-1369. (Last accessed in June 2020).

[Sheila Darmos] “The Southern Lights Project”, lectures and workshop, January 2020, online available at: http://thesouthernlights.org/. (Last accessed in June 2020).

[Ernst Götsch] “Syntropic Farm Project”, online available at: https://agendagotsch.com/en/. (Last accessed in June 2020).

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No matter your experience with waterproofing membrane failure, waterproofing breaches are not so easy to spot. In fact, according to one article in The Construction Specifier, the most minor-looking of leaks could be a sign. Depending on where and how the waterproofing was installed, that can lead to costly excavation work for basements, vaults, tunnels, and water features. It can also lead to full removal or replacement of fixtures and finishes in certain spaces, such as commercial kitchens and lobbies.

Still, that’s why envelope engineers or other professionals conduct site visits before construction is completed, right? They make sure the external waterproofing membrane is placed properly and effectively to mitigate the risk and damage of a breach as much as possible.

That can certainly lead to a relatively long-lasting waterproof structure. But it’s neither the most risk-free nor the most sustainable solution. But what does that mean for your architectural work? What does the risk and reality of external waterproofing membrane failure mean for you?

It’s Not Always Better to Stick with Technology You’re Comfortable With

Many architects like yourself are very familiar with external membranes. You know how to inspect and install them. You can physically see and touch them to sort them out before they’re covered. In short, there’s a sort of reassurance that comes with external membranes. You know they are actually there, and you know exactly what to do if any issues come up.

That comfort can be a detriment at times, however.

No Matter Your Comfort with Them, Membranes Are Still High-Risk

Sure, you can see the external membrane and know the ins and outs of it. But that doesn’t mitigate the risk of the membrane failing. If anything, too much confidence in it can stop you from trying out a less liable waterproofing system.

And even if you are able to physically check a membrane that’s been applied to the positive side of a structure and felt comfortable with that inspection, that doesn’t mean the membrane will stay that way. For instance, the backfilling process can easily tear the membrane. That can fail the whole waterproofing system right there as there is often no opportunity to excavate the membrane to repair it. As a result, builders often turn to epoxy injections to attempt to fix cracks and leaks that show up in accessible areas of a concrete’s surface. That still leaves water outside of those areas to continue passing through the concrete, threatening its structural integrity.

Too Much Confidence in Membranes Can Lead to Poor Concrete Construction

While we have talked about the risk that comes with membranes so far, that doesn’t mean they don’t have a place in construction. They certainly can be used effectively. But when they’re relied on to function perfectly by themselves and project stakeholders haven’t weighed the risks of their application realistically, it can negatively impact the quality of concrete construction.

Take the crack-bridging ability that some membranes have, for instance. Often, stakeholders in a project have full trust in this ability to cover cracks in concrete and prevent water from reaching those cracks. They make the assumption that this ability won’t fail. As a result, they feel less worried about having to face the consequences if concrete does crack. That leads them to care less about how concrete placement, curing, and control joints are handled.

Compounding this fact, stakeholders also highly regard the diversity of membranes available on the market. There are enough choices available that membranes seemingly come with an infinite number of different accessories to mitigate risks. But even with those accessories, membrane failure is still a possibility. Once that happens, those accessories aren’t going to stop a construction team from a long, costly repair process.

A membrane’s accessories might make that last situation seem highly unlikely. But unfortunately, that’s just not the case.

In Fact, External Waterproofing Membrane Failure Is Incredibly Common

As the Australian Institute of Waterproofing member Wet-seal notes, waterproofing makes up 80% of complaints during construction. It’s an impressive statistic considering waterproofing does not take up a huge chunk of the cost to construct a structure. Waterproofing typically only takes up 1% to 2% of that cost. So why are complaints so high?

A big reason for that is likely how easy it is for external waterproofing membranes to fail. It’s a pervasive enough issue that water intrusion is the cause for around 70% of construction lawsuits.

So, how does external waterproofing membrane failure get to be that big of a concern? Let’s look at the three most common reasons why.

One of the Main Culprits for This Is Simply Poor Preparation and Installation

At least 90% of waterproofing failures come from poor handiwork.

It’s not hard to see why either. Despite not being as costly as other parts of construction, waterproofing is no less complex. There are lots of factors to consider for it, and if one aspect isn’t considered carefully enough, a failure could be waiting around the corner.

Poor Preparation Is Often Due to a Lack of Time

Builders need to make sure the surface of the substrate they want to apply a membrane to has the following qualities:

A smooth and clean exteriorFalls for drainageA space absent of formwork distortions, voids, and protrusions

To achieve these qualities, they need to spend time and attention on looking to see if the substrate surface has been spoiled by debris and residue and whether they need to scrape and vacuum it. Otherwise, without a pristine substrate surface, it is likely that a waterproofing application will not be successful.

Poor Installation Is No Different

Builders have multiple items to install to ensure that a structure has an effective and thorough waterproofing system. Depending on the structure, that might mean knowing the correct installation procedure and executing it for the following products:

Waterstop anglesPerimeter flashingsVertical flashing anglesPressure strip flashingsChased drop flashingsControl jointsDrainage flangesCavity flashing downturnsReinforcing at junctionsOverflow devicesLinear strip drainsSlip joints

Not having the time to properly install even just one of these items can weaken the overall waterproofing system they’re a part of, making it more vulnerable to leaks.

In short, standing in the way of both proper waterproofing preparation and installation is time. Construction projects tend to run on tight schedules, so it can be tempting to skimp on the smaller details. Whether that’s quickly getting through backfilling and tearing a membrane unintentionally in the process or limiting quality assurance processes for faster work, it’s all done to help save what little time a project has. And while it might speed up a project in the short-term, the following repairs that result from this work will add up in the long-term to the project’s expenses.

The Second Culprit Is a Failure to Prime Areas Effectively

Waterproofing membranes, even self-adhering ones, require a primer during their application process. After all, builders want to ensure that their membranes remain bonded to a substrate for the life of the structure they’re waterproofing. And using a primer to prepare the surface of a substrate helps to enhance the adhesiveness of a membrane. It does so by reducing the porosity, dusting, air entrapment, and high-residual moisture of a substrate.

But it will only impart those qualities if builders prime the substrate surface effectively.

This is also an area that runs into issues with timing. When constructing homes, for example, a builder may not always accurately estimate how long it will take to prime the surface. As a result, they might schedule in tiling to be done in a bathroom and expect that the priming will only take a day or so. However, priming could take longer depending on the membrane, temperature, and weather conditions.

If the schedule is too tight, that could lead to a substrate surface with no priming, insufficient priming, or the wrong primer entirely. All of which can cause the membrane to debond. That creates gaps in the membrane system, leaving room for moisture to penetrate the substrate and weaken its structural integrity.

The Last Is a Lack of Insight into the Substrate’s Residual Moisture

Unsurprisingly, out of the top three common causes of external waterproofing membrane failure, moisture remains one of the bigger obstacles. All it takes is poor preparation, installation, or priming for moisture to enter the structure and wreak havoc.

But what if moisture was already surrounding the structure but had gone unnoticed? As you might have guessed by now, that’s a pretty common situation. And it likely stems from a lack of awareness at how much moisture content a substrate has.

Without an accurate estimate of moisture content using a tool like a moisture meter, there is a high chance that the substrate still has residual moisture. When left alone, that moisture can interfere with a membrane’s ability to bond to a substrate, causing structural weakness to occur.

That Puts Membranes in an Awkward Spot When It Comes to Sustainability

Because it is so easy to damage membranes through application alone and because that damage can have severe consequences for a structure, membranes should not be considered the ideal sustainable solution. After all, you can’t call something sustainable if it can’t be upheld safely in an environment for a long time.

Though, it is true that not all membranes are going to fail immediately during application or afterwards. What about those then? Would we call the ones that can last without wear and don’t hurt their environment sustainable?  It’s debatable, but in this instance, the answer would still likely be no. And that’s because many membranes come with a short life span of around one to 10 years before they deteriorate.

After that, they need to be replaced. If they aren’t, then water damage is a more likely possibility. And if they are, then the building’s maintenance team needs to use up monetary and construction resources to get the same waterproofing protection.

All in all, it’s a very short-term version of sustainability that is draining resources at regular periods unnecessarily as there are long-term forms of waterproofing out there.

Even Worse, Acquiring External Membranes Is Also Not That Sustainable

Even if you still want to stick with specifying and using external membranes, you may find it increasingly difficult to do so.

For One, There Is a Global Materials Shortage That May Hinder That

Between the ongoing pandemic, the past Suez Canal blockage, delayed and pricier shipping, and the mass blackouts in Texas that led to chemical plant shutdowns, there is a significant materials shortage going on.

And waterproofing membranes have not gone unscathed. Often made with plastics and other materials that typically require crude oil, membranes have been hit in both areas. Plastics are hard enough to get that companies like Acer and Dell are starting to create products with recycled plastic instead. Meanwhile, crude oil is in a different sticky situation. Instead of a shortage of the product itself, there’s a shortage of tanker truck drivers in the United States of America. At least 50,000 more drivers are needed. With the two materials harder to supply, that is going to make waterproofing membranes also harder to supply and will likely increase their costs as demand goes up for that shorter supply.

The general perception is that this might get better sometime in 2022 or a little later. But does that mean you should wait it out?

Even Without a Shortage, Membranes Will Still Be Non-Eco-Friendly

While only some membranes use plastic, almost all require crude oil in their manufacturing. And that doesn’t bode well for the environment. According to the University of Calgary’s energy education team, whether drilling for oil, transporting it, refining it, or using it otherwise, there is always an environmental impact. Extracting it, for example, destroys the land around it. And other oil industry activities can end up producing chemicals that contribute to smog or creating greenhouse gases that increase the effects of global warming. Moreover, if during any part of that process, the oil spills, it can impact the plants, soil, and well-being of animals, making the environment wholly toxic.

All of which is definitely not a way to maintain human well-being either, making membranes even less ideal for sustainability.

Nowadays, There Are Better Alternatives Out There

And they come in the form of crystalline waterproofing admixtures.

To apply these products, builders have one step and that’s it. There’s no detailed handiwork or long time period required. All builders have to do is add your specified admixture into the concrete mix. From there, the mix will have the waterproofing properties it needs. It’s a short and sweet process that should permanently waterproof a concrete structure without the risk of application error.

The only real challenge you’ll come across is finding which crystalline admixture is right for you.

Just Look Up Your Options for Concrete Waterproofing Admixtures

The American Concrete Institute has classified these products under two categories: permeability-reducing admixtures for non-hydrostatic conditions (PRAN) and permeability-reducing admixtures for hydrostatic conditions (PRAH).

The first of the two we recommend for low-risk use. PRANs, as their name implies, are not meant to handle heavy water pressure. Instead, they are more designed to repel water. To that end, they often use water-repellant chemicals. These might involve soaps, vegetable oils, or even petroleum. Such materials work to leave a layer alongside concrete pores that repels water while still leaving the pores themselves open. However, PRANs can also make use of chemically active or inert fillers, which act as densifiers to limit how much water gets into concrete pores. In either case, you don’t get watertight waterproofing with them.

What you do get is a solid dampproofing solution. So you could use PRANs for projects that will encounter a little moisture ingress. That might involve using them to repel rain off a structure or  to minimize the structure’s dampness.

So, what about PRAHs?

Now, these are what you should really keep an eye out for. These are recommended for long-term waterproofing against heavy water pressure. They tend to use a hydrophilic polymer plug or crystal technology. And that creates waterproofing that is impervious to damage or deterioration and capable of bridging cracks in concrete.

It makes PRAHs a perfect option for watertight waterproofing in any concrete structure.

(For even more details on these waterproofing admixtures and more, get our free e-book on the topic!)

We Recommend Krystol Internal Membrane

(KIM) for Thorough, Sustainable PRAH Waterproofing

If you want a specific PRAH recommendation, we suggest KIM.

When you specify it, KIM gets added to the concrete mix where it disperses Krystol technology throughout the entire mix. That way, once the concrete cures, the technology will rest dormant throughout the slab until it encounters water. Once that happens, the technology will activate and react to the water and nearby unhydrated cement particles to create interlocking crystals (which you can visibly see react in a sample via time-lapse here!). These crystals go on to fill up capillary pores and micro-cracks in the concrete. That blocks the water from passing through.

And it does that for the entire life of the concrete as KIM remains within concrete permanently.

So you get lifetime waterproofing for the simple act of adding KIM to a mix. There’s less labor involved and no installation risks, which will save your construction team time and money, expediting their work in the process. There are no shortage issues. And even better, KIM comes with several sustainable advantages:

Reducing site disturbance by eliminating the need for excavationEliminating any possible waste it has by coming in custom-size pulpable bagsContaining no volatile organic compoundsHaving NSF certification for safe use with potable waterEnsuring KIM-treated concrete can be recycled post-demolition

So when you use KIM, you can earn LEED points while also benefitting from less labor-intensive and time-consuming permanent, tear-free waterproofing.

Waterproofing Membrane Failure Is a Sign to Revolutionize Your Design

When you think about external waterproofing membrane failure and how common it is, consider what the alternatives are. There are many concrete waterproofing admixtures out there that could better solve the issues that come with membranes. And if you want one that gives you an edge in the LEED sustainability framework, you don’t have to look farther than KIM. It will revolutionize your architectural design and help it become the green watertight structure you’re looking for.

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