Tham khảo tài liệu 'biofuels, solar and wind as renewable energy systems_benefits and risks episode 2 part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 13 Bio-Ethanol Production in Brazil 339 Buildings are regarded as having a useful life of 50 years and a maintenance energy cost of 4 per yr Macedo 1997 . As the greatest energy input is in cement the energy value of this material is used. As fuel costs are such a large part of manufacturing costs most cement companies have aggressive energy conservation programs and according to the International Energy Program IEA 1999 new manufacturing plants have reduced energy use by between 25 and 40 compared to 10-15 years ago. The report by the IEA 1999 gives a value of GJ for the energy required to produced 1 Mg of cement and other recent reports Young et al. 2002 and Worrell and Galitsky 2004 give somewhat lower values of and GJ Mg-1. We use the former higher value of GJMg-1. So allowing for a 4 annual maintenance cost the total embodied energy for all buildings over a 50 year period is 1 600 X 50 X 1 600 U GJ which becomes 31 730MJ or . As we assume that the mill serves to grind one third of 2 million Mg of cane per year this becomes MJ Mg cane milled or MJ ha-1 yr-1 Table . For the mild steel in the mill distillery we have assumed that one third is in light equipment and thus subject to more wear and will have a lower useful life Table Energy in the buildings and construction of a standard mill distillery. Design capacity 2 million Mg year running at 33 capacity. Methodology for the calculation of the fossil energy inputs follows that of Pimentel 2007 Mass a Useful lifeb Including maintenancec Including on-site energy utilisationd per year kg ha year Total energy Mg yr Mg Mg kg kg MJ ha yr Cement in buildings 1600 50 100000 Mild steel structural 2873 25 244205 Mild steel in light equipment 1437 10 201180 Stainless steel 410 25 34850 Basic data on standard cane Factory Mg cane harvested by factory 666667 .
