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Integrated production systems

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Integrated food-energy system in Bogotá, Colombia

The Tosoly Farm in the Colombian foothills north of Bogotá, is a highly integrated farm that produces food and energy for family consumption and for sale in a crop and livestock system. The crop component is based on sugar cane, which is grown as feed for pigs, food and energy, and coffee and cocoa, which are grown for food and energy, and multipurpose trees. Sugar cane is cultivated on 1.5 hectares of the seven- hectare farm. Tree crops include coffee, cocoa, forage trees and forage plants for timber and fuel, for shading the coffee.

The livestock and fuel components are chosen for their capacity to utilize the crops and by-products produced on the farm. The sugar cane stalk is fractionated into juice and residual bagasse. The tops, including the growing point and some of the whole stalk, are the basic diet for cattle and goats. The juice is used as feed for pigs and the source of ‘sweetener’ for the farm family’s cooking. The bagasse is the fuel source for a gasifier that provides combustible gas for an internal combustion engine linked to an electric generator. The goats are the means of fractionating the forage trees, consuming the leaves, fine stems and bark as sources of protein. The residual stems are an additional source of fuel in the gasifier. The goat unit has ten breeding does and two bucks. There are three pens for two crossbred cows and their calves, which are kept for the production of milk, meat and manure. 

The pig unit has a capacity for 40 growing pigs and five sows. Forty hens and six ducks are raised for eggs and meat in foraging, semi-confined systems. Rabbit production, a new venture on the farm, applies the principles of 100 percent forage diets developed in Cambodia, the Lao People’s Republic and Viet Nam. 

A horse transports sugarcane and forages. All high-moisture wastes are recycled through plug-flow, tubular plastic (polyethylene) biodigesters. Pig and human excreta are the feedstock for four biodigesters. Waste water from coffee pulping, washing of dishes and clothes go to a fifth biodigester. Effluents from all eight biodigesters are combined and recycled to the crops as fertilizer. The pens for the goats and cattle have clay floors covered with a layer of bagasse to absorb the excreta. Periodically, this manure is applied to the crops as fertilizer and a source of organic matter.

Most of the energy on the farm (about 100 kilowatt hours per day) is produced by gasification of the sugarcane bagasse and the stems from the mulberry and Tithonia forages. The installed capacity of the photovoltaic panels is estimated to yield 8 kilowatts daily. The eight biodigesters produce 6 cubic metres  of biogas daily, two-thirds of which are converted to electricity (6 kilowatt hours per day) using it as fuel in the same internal combustion motor generator attached to the gasifier. The remainder is employed for cooking. Low-grade heat energy produced by the solar water heater and the wood stove are not included in the energy balance.

After deducting the electricity used to drive the farm machinery and to supply the house (11 kilowatt hours per day), the potentially exportable surplus is 104 kilowatt hours per day. At the current price of electricity (USD 0.20 per kilowatt hour), this would yield an annual return of USD 7 600. Annually, the gasifier produces 4.4 tonnes of biochar, which is returned to the soil. Assuming that 65 percent of carbon in the biochar is not oxidized in the soil (Lehmann, 2007), then the effective sequestration of carbon dioxide is in the order of 11 tonnes annually.

Source: adapted from Preston, 2010.