Biofuel co-products as livestock feed - Opportunities and challenges

50Biofuel co-products as livestock feed – Opportunities and challengesThe process of producing ethanol from algae beginswith growing starch-accumulating, filament-forming orcolony-forming algae in an aquaculture environment. Afterthe algae have been grown, they are harvested to providebiomass, and decomposition of the biomass initiated. Thedecomposition process can be done mechanically or nonmechanicallyto rupture the cells. Yeast is added to thebiomass to begin fermentation and convert carbohydratesto ethanol. Ethanol is then harvested after fermentationis complete. It is not known if the residual biomass fromalgae bio-ethanol production will have significant feedingvalue for animals. Additionally, there is research underwayto determine the feasibility of producing ethanol from seaweed,as well as combining cellulosic ethanol and biodieseltechnology in an attempt to gain greater efficiencies inbiofuels production than from those processes currentlybeing used.FEED AND FOOD SAFETY QUESTIONSWe are at a critical point in history, where intelligent decisionsneed to be made not only about the need to continueto develop and use new food production technology tofeed the world, but also to provide realistic risk assessmentof any potential short- and long-term consequences ofusing these technologies. For example, some countries haveembraced the use of genetically modified grains in animalfeeds and recognize them as safe. In contrast, other countrieshave been reluctant to accept the use of this technology,which consequently limits their choices and increasesthe cost of food.Several characteristics of DG have been identified aspotential animal or human health risk factors. However,knowledge, tools and product options exist to mitigate oreliminate many or all of the potential risk factors discussedin this section.Genetically modified grainsApproximately 98 percent of the maize produced in theUnited States is from genetically modified varieties. Farmersprefer to grow these varieties because of their better yields,whether economic or agronomic. As a result, maize seedcompanies are continually developing new geneticallymodified maize varieties that possess economically importantagronomic traits. For example, a new genetically modifiedmaize variety (Event 3272, released as cv. Enogen) hasbeen developed by Syngenta Seeds, Inc., with the goals ofimproving ethanol yields while reducing energy costs andgreenhouse gas emissions. The use of Enogen grain byUnited States ethanol producers could provide a 380 millionlitre ethanol plant with annual efficiency improvementsthat save 1.7 million litres of water, 1.3 GWh of electricityand 244 billion BTUs of natural gas, which is equivalentto the amount of power needed to heat several thousandhomes, while reducing carbon dioxide emissions by 48 000tonne. These are all very positive. Syngenta requestedthat the United States Department of Agriculture’s (USDA)Animal and Plant Health Inspection Service (APHIS) grantnon-regulated status to its alpha-amylase maize (‘Event3272’) in 2005. It was approved by the US Food and DrugAdministration (FDA) for human food consumption in2007, and in February 2011 APHIS announced its decisionto deregulate this new variety of maize, which has nowbeen cleared by USDA for production. However, it is importantto recognize that only a few thousand acres have beenplanted with this new maize cultivar, and only a few ethanolplants are involved in evaluating its potential benefits.What will be the acceptance of the maize by-products forfeed use in countries outside of the United States?SulphurSulphur is an essential mineral for animals and servesmany important biological functions in the animal’s body.However, when excess sulphur is present in ruminant diets,neurological problems can occur. When feed and water containinghigh levels of sulphur (>0.40 percent of diet DM) arefed to ruminants, a condition called polio encephalomalacia(PEM) can occur. PEM is caused by necrosis of the cerebrocorticalregion of the brain of cattle, sheep and goats, andif not treated with thiamin within 48 hours after the onsetof this condition, animals will die. Ruminants are more vulnerableto PEM when their diets are abruptly changed frombeing primarily forage to primarily grain based, causing ashift in rumen microbial populations to produce thiaminase,resulting in a thiamin deficiency. Sulphur appears to havea significant role and interaction with thiaminase productionto cause this condition, but the mechanism is not wellunderstood (Boyles, 2007). This condition does not occur innon-ruminant animals (pigs, poultry, fish).Sulphur levels can be highly variable among DDGSsources and can range from 0.31 to 1.93 percent (average0.69 percent) on a DM basis. Sulphuric acid is commonlyadded during the dry-grind ethanol production processto keep pH at desirable levels for optimal yeast propagationand fermentation to convert starch to ethanol, andis used because of its lower cost relative to other acids.According to AAFCO Official Publication 2004, p. 386,sulphuric acid is generally recognized as safe according toUS Code of Federal Regulation (21 CFR 582) and is listedas an approved food additive (21 CFR 573). In addition,maize naturally contains about 0.12 percent sulphur, andthis is concentrated three times like all other nutrientswhen maize is used to produce ethanol and DDGS. Yeastalso contains about 3.9 g/kg sulphur, and naturally createssulphites during fermentation.Table 8 shows examples of the impact on final dietsulphur levels of adding different dietary levels of DDGS,