Waste Transformation Through Closed-Loop Farming

This is a guest post by Paul Olivier, a US expat who lives in Dalat. His article Beyond the hype, a dirty side of Da Lat was published in December 2022 by VNExpress International.

No More Poverty and No More Pollution


Plants and animals do not appear separately within the natural world. Did you ever see an ecosystem consisting only of plants? or an ecosystem consisting only of animals? In the natural world we see multiple animal systems closely coupled to multiple plant systems. So simple and so obvious. That’s the way nature works.

Such interdependency and mutualism at the local level must also be extended to the raising of domesticated plants and animals. The large-scale mono-cropping of domesticated plants and the large-scale mono-raising of domesticated animals stand out starkly as gross aberrations within the natural world. Both are highly inefficient in producing food, and together they constitute one of the most destructive forces on our planet.

We must return to the concept of a multi-functional small-scale farm where multiple plant systems and multiple animal systems are closely integrated on the one farm. When this happens, small farmers are able produce all the feed and fertilizer they need without any external input of commercial feeds and chemical fertilizers typically brought in from thousands of kilometers away.

When small farmers are able to produce feed and fertilizer in abundance, they can make money as never before, since many levels of parasitic buying and selling are eliminated. Since the production of food is localized, small farmers can sell food directly to nearby households and restaurants without a single trader, middleman, market, supermarket or farmers market involved. In the end, there is an abundance of safe food at affordable prices at the local level, and the pollution and disease associated with biodegradable waste are eliminated.

The Four Levels of Waste Transformation

As odd as this might sound, it’s all about waste. It’s all about transforming waste at the highest possible levels. It’s all about shuffling transformed waste back and forth between multiple plant and multiple animal systems on the one farm. It’s all about creating food cascades and loops that are infinitely self-renewing. Here not a gram of waste is wasted, and biodegradable waste, in all of its many forms becomes the most valuable resource that small farmers could ever possess.

But before small farmers can tap into the bounty that waste has to offer, there’s a waste hierarchy that they should recognize and respect. Let us distinguish four different types of biodegradable waste in descending order of nutrient content.

Type 1 waste is waste biomass or co-cropped biomass rich enough in nutrients to be used as feed. Heat-treatment and/or fermentation are the most obvious ways to transform this type of waste safely into feed.

Some examples of Type 1 waste: food waste, slaughterhouse waste, crustacean waste, fish by-products, fish mortalities, fruit and vegetable waste, coffee pulp, banana stem, cashew apples, passion fruit peel, brewery and distillery waste, peanut press cake, bone, feathers and hundreds of other waste resources. Food waste sits at the top of this list, since about 1.3 billion tons are produced globally each year.

Type 2 waste is simply the fresh manure of the animal that ate the feed. Here fresh manure is collected off odorless, fly-free bedding. It is then fed to larvae of the black soldier fly. Mature prepupal larvae have a protein content of about 42% protein, and a fat content of about 34% – fats containing more lauric acid than coconut oil.

When larvae eat fresh manure, not a drop of leachate is produced. Nothing turns anaerobic and stinks. Their residue becomes a great substrate for red worms or nightcrawlers. BSF residue enables worms to grow two to three times faster than they normally do.

Type 3 waste involves mesophilic and thermophilic composting. The urine of the animal that ate the feed gets mesophilically immobilized in biomass bedding containing biochar. Nitrogen emissions and odor are completely suppressed. Type 3 waste also consists of green waste that cannot be used as feed or fed to larvae. This green waste, mixed with copious amounts of biochar, is transformed into compost by means of thermophilic microbes.

Type 4 waste consists of agricultural by-products and forestry debris that do not easily compost. It also includes invasive plants such as Mimosa pigra, mesquite and Chinese Tallow. Invasive plants can be harvested and gasified as a powerful means of controlling their spread.

At Level 1, small farmers produce feed derived from hundreds of different waste biomass streams. At Level 2, small farmers produce larvae (feed), worms (feed) and vermicompost (fertilizer). At Level 3, small farmers produce mesophilic and thermophilic compost (fertilizer). At Level 4 small farmer produce high-grade heat and biochar. Small farmers should not sell the intermediate products of feed, fertilizer and biochar. They should use them to create additional value on their farms.

Using combined heat and biochar gasifiers, small farmers simultaneously produce syngas and biochar. They do not have to buy fossil fuels, wood or charcoal to create high-grade heat. They do not have to chop down trees to cook, boil, sanitize, dry and so forth. And since biochar is a co-product of creating high-grade heat, farmers need never employ dirty biochar kilns that typically waste syngas and heat. See Combined Heat and Biochar Gasification.

The biochar produced at Level 4 is put into feed at Level 1 and into bedding at Level 3. Biochar in feed ends up in manure at Level 2, where it gets consumed sequentially by larvae and worms, and undergoes powerful sanitization. Larvae, worms and composting microbes also effect the surface oxidation and activation of biochar. When biochar is incorporated into bedding (about 10% by volume), it suppresses odor and provides enormous surface area for composting microbes. Up to 50% of a green compost mix might consist of biochar.

It is absolutely imperative that agriculture be de-industrialized and taken out of the hands of large companies selling feed, fertilizer, fuel and biochar to small farmers.

The Multifunctionality and Marvel of Biochar

Biochar produced at high temperatures has a surface area that ranges from 250 to 650 square meters per gram. Such a large surface area provides fermentation microbes, the gut microbes of poultry and animals, the gut microbes of larvae and worms, composting microbes and soil microbes – all with a lot of space for mutualistic exchanges within biofilm.

When biochar is incorporated into fermented feed at Level 1, we see increases in poultry, animal and fish growth ranging from 17% to 40%. When biochar finally makes its way into the soil, we see increases in plant growth ranging from 30% to 400%. Biochar produced at high temperatures (>800 C) can retain almost six times its weight in water and greatly reduces the need for irrigation. Biochar remains in the soil for hundreds to thousands of years. It’s a wonderful way to sequester carbon.

In the United States, a high-quality biochar can retail at times for over $2.20 US per kg. In Australia, biochar can sell for as much as $12 US per liter. In Singapore, biochar retails at times for over $20.00 US per kg. One hundred grams of high-quality bamboo biochar, used as an ingredient in bread dough, sells in Vietnam for 100,000 VND or $4.16 US. Since biochar is worth a lot more than the low-grade biomass from which it is derived, the cost of high-grade heat is less than zero (a profit).

The Hazard of Solid Fuel Combustion

Globally, 40% of the population (3.1 billion people) still rely on solid fuel combustion for cooking. According to the World Health Organization, the air pollutants released from solid fuel combustion account for 7.7% of global mortality (4,300,000 people). This is more than the sum of all deaths from malaria, tuberculosis and HIV/AIDS. According to the WHO, air pollution from household solid fuel combustion is the most important global environmental health risk at this time.

Household air pollution makes its way into the environment and contributes to ambient air pollution. Here it kills an additional 400,000 people each year. This is equivalent to 12% of total ambient air pollution related mortalities. Firewood-based cooking methods are responsible for 3% of global CO2 emissions, 25% of global black carbon emissions and over 1.3 billion tons of annual wood fuel consumption. Firewood-based cooking methods give rise to massive deforestation.

Field Testing of this Combined Heat and Biochar Gasifier

The World Health Organization defined what is safe and what is not safe in terms of particulate matter, carbon monoxide and benzene emissions. Alli Devlin did field testing of the 150-500 CHB gasifier. She measured and observed, using laboratory instruments in rural Laotian kitchens, that this gasifier controlled PM2.5 emissions at only 37% of the recommended WHO safe limit, and that it controlled CO emissions at only 9% of the recommended limit. In vented kitchens, this gasifier controlled the CO2 levels at 30% of the recommended limit.

The modified combustion efficiency of this gasifier was almost 1 (0.941), and the specific fuel consumption just 11% greater than LPG. The gasification of rice husks was only slightly less clean than LPG, but always within WHO guidelines.

In comparison to firewood combustion, this gasifier reduced PM2.5 emissions by an incredible 92.5%. In comparison to charcoal combustion, this gasifier reduced benzene emissions by 74.5%. In comparison to traditional cookstoves using firewood, specific fuel consumption was reduced by 62%. In comparison to traditional cookstoves using charcoal, specific fuel consumption was reduced by 36%. Cooking time was reduced by an amazing 50%. For further explanation of Ms. Devlin’s work, see The Role of Small-Scale Crop Residues in Southeast Asia’s Clean and Improved Cooking Sector.

Vietnam has enormous quantities of Type 4 waste that could easily meet, many times over, its demand for high-grade heat and biochar. Vietnam produces annually 97 million tons of rice straw and 9 million ton of rice hulls (Energy Potential of Agri Residual Biomass in Southeast Asia with the Focus on Vietnam). Both straw and hull are excellent gasifier fuels, and insofar as they are used as such, the useless and highly problematic burning of these crop residues can be eliminated.

Lam Dong province has 50,000 hectares of pine forests that are subjected to controlled burns each year. This burning gives rise to enormous air pollution. At times, the entire city of Dalat is completely covered in smoke. However, a fair portion of this forest debris could be pelleted and used as gasifier fuel, and the biochar produced could be returned to the forests, as explained in Forest Management.

The Enormous Value of Waste

If fish swim outdoors in streams or rivers, their waste cannot be accessed and directed to the growing of plants for human consumption. Aquaponics solves this problem. Fish are enclosed in tanks or ponds so that their fresh waste can be accessed and immediately directed to growing plants. For every one kg of fish produced aquaponically, about 12 kg of vegetables are produced. The waste of a fish over its lifetime can generate a lot more value than when that fish is sold.

Likewise, the waste of an animal, when properly transformed, can generate far more value over its lifetime than when that animal is sold. If animals are housed indoors on spacious, odorless and disease-free bedding, their urine gets rapidly immobilized within bedding and can be used as fertilizer. The spent bedding of about 45 indigenous pigs can keep a hectare of farmland well fertilized.

At the same time, high-quality feed in the form of larvae and worms, and high-quality fertilizer in the form of vermicompost, can be produced from fresh manure collected each day off bedding. For every 5 or 6 kg of fresh pig manure, there are sufficient nutrients to cultivate about 1 kg of larvae and about a 1 kg of worms.

Eliminating Trophic Levels

Eliminating trophic levels, whenever possible, can greatly increase revenue. Instead of feeding BSF residue to worms, farmers can feed it to aquatic bottom-feeders such as shrimp, prawns or crawfish – as their principal feed. The waste of aquatic bottom-feeders can be fed to bloodworms, and blood worms can be fed to poultry and certain animals.

Instead of feeding Type 2 waste to larvae and worms, farmers can feed it directly to certain fish. The manure of one dairy cow, for example, can produce over its lifetime about $8,900 US in fish and vegetables.

In Can a Cow Produce 100 Pounds of Pig Feed a Day?, we see that cow manure is an energy source for pigs, it provides protein and essential amino acids for pigs, and it provides micronutrients and vitamins, especially from the vitamin B group (including B12). About 40% of a pig’s diet might consist of cow manure. “Depending on several factors, one cow can provide food in the form of manure for 3, and up to 17 pigs.”

However, if cow manure would be fermented with molasses and other key ingredients, one might expect to see much better numbers than outlined above. Furthermore, pig manure can be fermented and fed to chickens, and chicken manure can be fed to certain fish. The waste of the fish can be used to grow plants aquaponically. Obviously, cow manure should not be directly burned as fuel or routed to biodigesters.

Poultry and Animals on Bedding

Not raised on concrete, and not let loose outdoors, there is most definitely a Third Way wherein poultry and animals are raised indoors on bedding and are accorded comfort and dignity throughout their entire lives. When housed on bedding, a sow and her piglets can even engage in building a nest. In this picture you see pigs that were raised right within the city of Dalat. No one ever complained about odor or flies. Raising pigs in an urban setting can greatly reduce the cost of transforming and transporting food waste.

Pigs and bedding are lightly sprayed each day with a probiotic liquid. Pigs can enjoy a level of hygiene that surpasses ordinary human hygiene. There is absolutely no smell, no flies and no disease, and therefore, antibiotics and other pharmaceutical need never be used. Pigs root and dig in bedding. They run and play on bedding. They even eat bedding. When raised in this way, there is no stress and no anti-social behavior. Please watch this video of happy pigs.

The Localization of Food Production

Food is not a just another commodity to be traded in the global marketplace. When all of the environmental, economic and social benefits of waste transformation are correctly factored into the production of food, food is a lot more than the nutrition it provides. If waste transformed locally is the best thing we’ve got in producing food, so too, food produced locally is the best thing we’ve got in dealing with certain types of waste at the local level.

All nations must learn to deindustrialize the production of food, to localize the production of food and to decommodify the sale of food. How else can they achieve food security in the context of political instability, war or climate change?

The market value of food should never override broader issues relating to food safety, food security, food justice, food sovereignty, income inequality, the health of the environment and the biodiversity of our planet. Since no country should depend on another country to transform its waste, no country should depend on another country to produce its food.

Human Waste

When human waste is correctly transformed and safely returned to agriculture, sustainability kicks in as never before in modern times. The high-level transformation of human waste is not optional. It is absolutely necessary if ever humans are to live in harmony with the natural world. “For 4,000 years, human excrements and urine were considered extremely valuable trade products in China, Korea and Japan (Recycling animal and human dung is the key to sustainable farming).” If human waste is not properly transformed, agriculture will always be dependent on chemical fertilizers full of arsenic, cadmium and other heavy metals.

To achieve sustainability in an economical, safe and efficient manner, all toilets should be no-mix dry toilets, and septic tanks and sewage treatment plants that waste human waste and precious water resources should be done away with. No-mix, dry toilets can be fabricated for less than $30 US. They are lightweight and portable, and can be situated anywhere in a house that privacy permits.

The dry toilet shown here is used in conjunction with a hand-held urinal. Not mixing urine and feces allows for a lot more possibilities in safely and effectively transforming these two waste streams.

Human urine can be routed to duckweed ponds. Duckweed is one of the fastest growing multi-cellular plants on earth. Under the right conditions, it can double in mass in less than 24 hours. It can yield up to 182 dry tons/hectare/year. By contrast, the yield of soybean is typically not more than 4 tons/hectare/year. The crude protein content of duckweed can reach as high as 42%. Duckweed makes an excellent feed for pigs, poultry and certain fish. Moreover, duckweed protein closely resembles animal protein.

Another option: urine can be poured into a mixture of relatively dry biomass and biochar, and composted in the same way as pig urine in bedding. There nutrients within urine get quickly immobilized, and odor is completely suppressed. The urine of a few households immobilized in this way with biochar can easily fertilize about a hectare of farmland.

Rice straw, together with a bit of urine, can be fermented and fed to cattle. Human urine can undergo struvite precipitation to form a great slow-release fertilizer. Some households even route human urine to grow beds to grow all the vegetables they need (Anthroponics).

Human feces can be fed to BSF larvae, and the waste of the larvae can be fed to worms. Larvae and worms can be fed to chickens or fish.

Another possibility: human feces can be stored in an aerated outdoor bin together along with an equal volume of biochar. After a few months of storage, it solidifies into a stone and can be pulverized and used as fertilizer.

By the way, when human feces is stored indoors in a feces pan, and when an equal volume of biochar is applied to it each time it is generated, odor is completely eliminated. Back in the 1850’s, the father of organic chemistry, Justus von Liebig, argued strongly against the use of flush toilets, saying that charcoal can easily the eliminate odor of human manure. For more explanation, please see this presentation on urine-diverting dry toilets.

We talk a lot about sustainability. But we will never achieve sustainability until we learn to give back to nature in a closed loop everything that she needs to sustain us. Giving back to nature all the nutrients within our own waste is our first and most important duty as citizens of planet Earth.

Small Farmers in Social Enterprises

Small-scale, multi-functional farms can be ten to a hundred to a thousand times more productive and lucrative per hectare than large-scale mono-functional farms, and when small farmers are incorporated into social enterprises that educate, train, equip and sell on their behalf, small farmers in developing countries, with no more than a hectare of inter-cropped farmland, can each make a minimum of one billion VND or $40,000 USD each year.

When small farmers can earn substantial money on their farms, their children will not migrate to large cities to work as slaves in shoe factories and the like, extended families will not be split apart, and cultural traditions that define the uniqueness of a people over many centuries will remain intact.

If small farmers provide land and labor, they should receive 80% of the profit when their food gets sold. The social enterprise then carries out the home and restaurant delivery of food on their behalf, and in so doing, it earns 20% of the profit. (Imagine 100 small farmers in a social enterprise each producing on average one billion VND of food each year, and the people running the social enterprise receiving 20 billion VND each year.) Markets, supermarkets and even farmers markets are not needed. Since it has no employees, a social enterprise does not need to be unionized. Even though it is not a charity, it stands as a staunch defender of economic and environmental justice.

In this way, small farmers make a lot of money, and the people running a social enterprise are engaged in a highly profitable business. At the same time, farmers would not have to lose time transporting and selling their food, and consumers would not have to waste time and resources cluttering streets and highways in traveling to markets, supermarkets or farmers’ markets to buy food.


When people let waste go to waste or fail to transform it at the right levels, the environment inevitably gets polluted, the beauty of the natural world is destroyed, and people often go hungry and are malnourished. How often do we see pictures of starving or malnourished children sadly surrounded by filth and waste? We do not have a food crisis, but a catastrophic failure to grasp the basics of waste transformation.

The natural world is prepared to give us all the food that we need. We have only to give back to her the transformed biomass that she needs. Giving and taking must be in balance so as to create infinitely self-renewing food cascades and loops. We need a global revolution in agriculture in which social, economic and environmental justice prevails.

Imagine a world in which there is no more poverty, no more pollution, no more hunger and no more malnutrition. Imagine a world in which Big Ag is relegated to the trash heap of history. Imagine a world in which traders, middlemen and loan sharks are totally out of the picture. Imagine for a moment the beauty of a planet not defiled by trash and waste.

Marvelous things happen when humans do not waste waste, and when they live in harmony with the natural world. For a lot more explanation, please see Waste Transformation Closed Loop Farming.

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