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Montfort Boys Town, Fiji: Beer Waste into Mushrooms, Fish, and Vegetables

George Chan, an advocate of integrated farming with 40 years of experience, proposed an early ZERI project in Fiji. Sludge from a local brewery was used to create revenue-generating products—mushrooms, pigs, chickens, fish, vegetables, fruit, and fuel for electric power.

The site for his experiment was Montfort Boys Town, a school for disadvantaged boys, who had traditionally raised food and money by farming fish in ponds. ZERI chose Fiji both because it is poor and because its one main industry—sugar—was in decline.

The brewery provides the waste of spent grains for free. Farmers tried using the waste for feed, but it was difficult for animals to digest. Once dried and mixed with rice straw, newspaper, or sawdust, the waste is an excellent substrate for mushrooms, which are grown on shelves in a traditional, one-room thatched hut constructed by the boys. Chan had hoped to use native mushrooms, but as none were readily available when the experiment was launched, he selected three kinds based on the climate and conditions—shiitake (Lentinus), oyster (Pleurotus), and straw (Volvariella), each of which grow well by digesting the spent grain.

In traditional mushroom farms, the digested substrate is dumped on fields, where it can overwhelm planted crops. At Montfort, the boys shovel it into pails and carry it to a nearby wooden shack where, thanks to the work of the mushroom enzymes, it is now nutritious and digestible feed for a second revenue-generating product—chickens and pigs.

Every couple of days, the waste from these animals is flushed with water into a closed concrete and metal drum called a “digester.” Anaerobic bacteria break down the animal waste, giving off methane gas—a third product—which is piped off and collected in bottles. The gas is used to power the school’s lights and to steam the mushroom substrate.

The solid waste is further digested as it travels through several compartments where 60% of its biological and chemical oxygen demand is removed. Then the substrate is gravity fed into a series of three algae ponds in which bacteria, plankton, and other micro-scavengers aerobically consume the remaining unwanted parts of the original animal waste. The animal waste has then been converted into algae, which is harvested and used as high quality compost for the vegetable and fruit crops—a fourth product—that grow on the dykes surrounding the fish ponds, as well as for fish food.

Chan’s fish ponds—the fifth product—have seven kinds of fish from top feeders to mud carp and scavengers, creating an ecology of its own that eliminates the need for the antibiotics and frequent cleanings needed on traditional fish farms.

In addition to the flowers, strawberries and other vegetables grown around the ponds, additional crops are grown on top of the pond, hydroponically, again providing food, income and experience for the Montfort students.

Due to the success of the project, Montfort Boy’s Town has now created a center for sustainable development from its former vocational training school. Its students are steeped in a curriculum of hope, graduating with experience and knowledge of how systems can be designed to create abundance from waste while simultaneously enhancing the environment.

Tsumeb, Namibia: Brewery Moves to Fish Ponds

Impressed by the early results of Chan’s work, a commercial brewery in Tsumeb, Namibia, relocated its facilities to farmland that provided space next to the brewery for two fish ponds, a pen for livestock, and a biodigester to process the animal waste. The 3,500 square-meter ponds produced 10 tons of fish per hectare.

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