ENERGY 362 63 LANDTECHNIK 6/2008
Biogas in Brazil B razil is the fifth largest country in the world and with its acreage of 8.5 Mio. km 2 it covers almost the half of the South-American continent. In 2007 the country provided 46 % of its energy by renewables, mainly from sugar cane and its derivates (e-thanol, bagasse, vinasse), hydropower and wood . Alarmed by energy shortages in the past, the Brazilian Government tries to ensure an economical power supply all over the country. The biogas technology can contribute to this
... contribute to this considerably. History of agricultural biogas plants in Brazil Already in the 1970s and 1980s the interest for biogas in Brazil was raised, especially for swine farmers. Agendas from the government tried to reduce the dependencies of small and rural farms from mineral fertilizers and energy. As well they tried to decrease the damaging effects of animal farming to the environment and to raise the income of the farmers. But these expectations were not fulfilled and the biggest part of the plants was abandoned . Reasons for this failure were • the lack of know-how about design and function of the biogas plants • high costs for construction and maintenance of the plants • deficient know-how about land use systems , their nutrient demands and the balance • missing information about the nutrients in the digestate • rising costs caused by the need of purchasing new machines for transportation and application of the digestate • missing methods for conditioning of the gas • no adapted technology and due to this short durability of the used aggregates • wrong dimensions, designs and use of the plants • availability of cheap electric energy and liquid gas Currently the Brazilian electric energy supply is based to 77 % on the hydro power, which is susceptible to fluctuations (Fig. 1) . In 2001 the phenomenon of the "Apa-goes", the cut off of the electrical power in a large scale appeared in Brazilian cities due to acute energy crisis. Therefore the biogas plants once more got attention. But when the danger of the "Apagoes" was over, the projects to build biogas plants were cut off, and those that were already started to build were abandoned. In the last years, with the implementation of the emission trading, the biogas plants appeared again . Today, 30 years after the failed experiments to implement agricultural biogas plants, this technology offers the Brazilian farms a perspective again. Reasons for this are the ability of new materials, the raised dependency on energy, because of higher automation at the bigger farms as well as the rising prices for conventional energies. The possibility to generate income from emission trading affects this . Especially in poultry farming this technology will gain Due to negative experiences in the past, biogas technology could not establish itself in Brazil. Currently though, there is a revival of agricultural biogas plants there. Biogas production from animal residues is especially suited for the southern regions, where swine and poultry farms are concentrated. Generally the Brazilian plants are small and simple units, which cannot be compared to those in Germany.Vinasse, a fluid residue from alcohol production with high potassium content, is generally used as fertilizer on sugar cane fields. Using vinasse as a substrate for biogas production would be very recommendable, but is seldom done due to lacking general political conditions and technology.