Biogas technicians Josephat (left) and Lewis uncovering a standard Flexi Biogas system.

Advancing sustainable agriculture and waste management using flexi biogas technology

By Joseph Macharia

One of the dangers staring at humanity is effect of the enormous waste we release every day. Millions of tons of both organic and inorganic waste end up in dump sites, worse still in our water bodies. Only a tiny fraction of this   waste   is  recycled or harnessed to produce clean energy.

Copycat Farm, a farm specializing in innovative sustainable farming solutions has come up with biogas systems that not only convert  waste into energy but also organic fertilizers.  The farm is situated in the outskirts of Nairobi in Karen. To them, organic waste is   a resource that if tapped into,  can eradicate poverty, increase food production  and  at the same time help conserve our environment.

At a time when the cost of electricity and fuel is  going up, biogas presents a viable solution for producing energy for domestic and industrial use cheaply. However, the traditional biogas systems  are not used by many people because they are expensive to set up.

Flexi biogas

Under their business arm, Biogas International, the farm has developed an innovative flexi  biogas solution to tackle waste management sustainably. It’s a new innovation in biogas technology that does not require construction or digging like the conventional biogas systems. The system imitates nature’s digestive system: It has a mouth (or the inlet), the digester which does the same function as the stomach and finally the outlet.

The stomach is made up of an elastic tarpaulin material that can last for  fifteen  to twenty   years. On top, it’s normally covered with green house cover which warms the digester facilitating rapid breakdown of wastes.

Traditional biogas systems are dug underground hence  the   waste  is    broken down slowly because of cold. Flexi biogas systems on the other hand are installed anywhere, on the ground, on a raised platform or on roof slabs which makes gas production to be at optimum levels.

Not only is   biodegradable waste like animal dung  used, kitchen waste, food remains and invasive plants like water hyacinth and cactuses can also be used. With flexi biogas, one does not have to own a herd of cattle nor build capital intensive construction.

“Green waste will  be   five times more productive  than animal dung ,  while  food waste  with fats will produce almost tenfold,” Lewis Ngugi, communication officer at the organization says. When broken down, oils and fats produce more gas because of high calorific value.

All the waste is fed into the biogas system through the inlet, after which breakdown of the waste starts immediately.  The gas is then harvested and piped for storage. You can tell how much gas you have by how the digester bag is swollen. At the outlet, rich liquid organic fertilizer is collected.

Vegetables planted on vertical gardens and are irrigated using drip with rich bio organic

Harnessing invasive species

Water hyacinth has long been a menace at Lake Victoria. It   causes   a lot more harm than good. The invasive weed is an interesting plant: If you plant it in a pond it will not grow. It thrives where water is polluted sucking up nutrients. Shockingly, it multiplies rapidly in a matter of days. With flexi biogas, water hyacinth can be used as a resource to generate energy and produce rich organic fertilizer.

“Once we put water hyacinth in our biogas system, we get the energy and recover the nutrients, which the hyacinth had absorbed from the water and the nutrients are then used for food production. It becomes an energy resource, because it grows very fast on polluted water,” Ngugi observes.

They have since installed large capacity biogas system, the T-rex digester in Kisumu, Dunga beach to manage water hyacinth, fish offals and hotel waste. Similarly, they have constructed over fifty domestic units to help residents capitalize on water hyacinth, thereby helping in reducing pollution and in conservation of the environment.

Cactus that has taken over grazing land in Northern Kenya is also used as a feedstock for their biogas in those regions making it an invaluable energy and fertilizer resource.

Flexi biogas models

Flexi biogas digesters come in various sizes and capacities. They have the standard model (6m3), measuring  two by six  metres. It is designed for a small family of  four to six  people. The whole package consisting of the digester, greenhouse and shade-net covering, piping, double burner stove and installation costs at Kshs. 80,000. This system takes in  twenty  kilograms of waste to produce all the gas required for a typical family.

There  is   a larger model – XL model (9m3) for relatively large families of  eight  to  ten  people. It measures  two  by   eight  metres.   Apart from supplying the energy for domestic cooking, the XL digester produces extra gas that can be used to power other appliances such as water heater /shower. It goes for Ksh. 95,000.

XXL model digester (15m3) which measures  two  by  twelve  metres   is another model. The system has the capacity to meet the cooking energy requirements for a household of up to  fifteen  members. It has capacity to power ovens and incubators. The more gas you  generate, the more appliances you can power and the more money you can save or generate.

They also provide commercial biogas system called the T-rex for large capacity use. This system comes in various models: 30m3, 60m3 and 100m3. The systems are scalable to meet any energy demand and they are best suited for hotels, schools, farms and areas with high energy demand.

Human waste management is also one of their offerings. They use bio-san system which requires no digging. Since the human digestive system takes in almost all the nutrients from the food we eat, what exits our systems has little biogas potential.

The bio-san system breaks down the human waste into liquid, which is then channeled in shallow drains called ‘French drains’ and directed into lawns, or along the fence for growing hedges. But the system never fills up neither requires emptying.
Circular economy

After you install the biogas you can use the rich organic fertilizer to nourish and put back nutrients to the soil and plants effectively, achieving a circular economy. “Plant wastes go into the biogas, you harvest energy. Then the nutrients that crops had pulled from the soil are harvested as liquid fertilizer and taken back to the plants,” explains Ngugi.

Lewis Ngugi posing beside a T-rex biogas system.

In fact, Ngugi says the whole thing can be automated, taking less than  five   minutes to irrigate a garden. Instead of having someone watering the crops, the liquid organic fertilizer is collected, piped to a raised tank where it is   mixed with water before being fed to the crops using drip irrigation.

Households without space can make vertical gardens and plant vegetables to reduce their  costs on food. Can it be done on large scale? A resounding yes! They have worked with farms, schools and institutions and hotels where they’veinstalled these solutions . “  These   institutions  have realized reduced energy costs and fertilizer inputs, “  Ngugi testifies.

Zero waste

Biogas International has partnered with Kajiado, Kisumu and Nyeri counties to help manage waste. For instance, in Ngong town they manage all the waste produced in the market, the brunt of it being organic waste, which is turned in to biogas, liquid fertilizer and compost.

About  twenty  to  thirty   percent is glass, plastics and ceramics which they stock pile and sell to mainstream recyclers. The remaining waste   ( which is   wet waste   like diapers and pampers )   is  burnt in an incinerator at very high temperatures and turned to ash. But by the end of it all there is no waste to take to dump

Flexi biogas can be reached on: 0722 700 530



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