Seite - 130 - in Water, Energy, and Environment - A Primer

pellets are the most common type, but grasses can also be pelletized. Pellets are extremely dense and can be produced with a lowmoisture content that allows them to be burnedwith a high combustion efficiency. Furthermore, their uniform shape and small size facilitate automatic feeding. Woodpelletmarkets are of two types: industrialwoodpellets that are used as a substitute for coal in power plants, and pellets used in pellet stoves and pellet boilers for heating. A broad range of pellet stoves, central heating furnaces, and other heating appliances has been developed andmarketed since the 1980s.According to the IEAwood pellet productionmore than doubled between2006 and2010 (tomore than 14million tons), andwas expected to keep growing. For awhile this growthwas challenged by a series of warmwinters in Europe compounded by low natural gas prices. Nevertheless, fully automatic high-efficiency wood pellet boilers are common in Europe and they are beginning to penetrate markets in the US and other countries. The Asia-Pacific region will occupy more market share in future years, especially in China, as well as India and regions inSoutheastAsia. 8.5.3 Biofuels Another important applicationofbiomass is its direct conversion into liquid fuels (biofuels), which can replace petroleum- based fuels such as gasoline, diesel and jet fuel. These ‘alternative’ fuels fall into two categories: first-generation biofuels, such as ethanol, that are derived from sugarcane and corn starch (and therefore compete with food crops); and second-generation biofuels that use as feedstock non-food and low-value agricultural andmunicipal wastes that are not edible. Production of first-generation biofuels is well underway in Brazil and the US, but second-generation production is still limited by high production costs. The problem is the difficulty in breaking down and chemically converting – at a competitive Water,Energy, andEnvironment–APrimer130