Biofuel co-products as livestock feed - Opportunities and challenges

Utilization of co-products of the biofuel industry as livestock feeds – a synthesis 515ing trypsin inhibitors and lectins) is also available in Mexico.The heated kernel meal of this genotype is also an excellentfeed resource (Makkar, Kumar and Becker, 21). Sincejatropha meals are rich in phytate, addition of phytase inthe diets of monogastric animals is necessary for effectiveutilization of the meals.Crude glycerine derived from the production of biodieselfrom pure or waste vegetable oil or rendered animalfat can contain between 38.4 and 96.5 percent glycerol,although the normal range is between 75 and 85 percent(Mjoun and Rosentrater, 23). The large-scale biodieselproducers supply high grade glycerol to the food, pharmaceuticaland cosmetic industries, while that from the smallerproducers is likely to contain more impurities, thus limitingits usage. Animal fat derivatives contain less glycerol andmore impurities than from vegetable oil feedstocks. Trialswith channel catfish and rainbow trout have shown thatglycerol can be added to the diet at 10–12 percent and actsas a precursor for gluconeogenesis, but not lipogenesis.However, rainbow trout do not use glycerol efficiently as anenergy source (Mjoun and Rosentrator, 23).MICRO-ALGAEAll of the feedstocks considered above have been producedfrom agricultural land, either suitable for croppingor currently regarded as marginal. Phytoplanktons are thelargest biomass producers in global aquatic systems, bothmarine and freshwater, at levels that sunlight can facilitatephotosynthesis. Algae, the primary producer, are responsiblefor half of the annual global output of organic carbon(Ravishankar et al., 24). The viability of biofuel productionfrom micro-algae depends on full use of the algal biomass,which is rich in proteins and vitamins and therefore usefulfor food and feed. They contain chemicals, pigments, fattyacids, sterols and polysaccharides. They have anti-viral, antitumourand anti-bacterial properties and act as an antidoteagainst HIV. Their ‘farmed’ production could be centred oncoastal seawaters, thus removing competition for land andwater resources needed for agriculture. Ravishanker et al.(24) propose five areas to be considered in developing theiruse: (1) algal biodiversity; (2) large-scale culture of microalgae;(3) downstream processes for conversion to biofuels;(4) use of micro-algae for food and feed; and (5) technicaland economic analysis of the bio-refinery concept to assessand promote adaptation. Algae thrive under a wide rangeof extreme conditions and have simple nutrient needs anda very fast growth rate, with the ability to accumulate fatup to 50 percent of the their biomass. The authors describetwo methods of cultivating micro-algae, either in openponds, which are relatively cheap and most of those useddo not compete for land, or in closed system cultivationthat can be more closely regulated (Ravishanker et al., 24).Algae yield biofuels (diesel) by trans-esterification of algallipids or hydrocracking (i.e. cracking and hydrogenation ofbiomass containing hydrocarbons). Ethanol can be releasedfrom either algal biomass or algal cake (Ravashanker et al.,24). In Table 6 of Chapter 24, the authors give the foodapplications for micro-algae, together with the cultivationsystem and the countries currently involved, and in Table 7compare the vitamin content of some algae with traditionalfoods. Many micro-algae contain vitamin B 12 and somebrown algae contain tocopherol. Micro-algae containingastaxanthin are also used as feed in aquaculture production,where they can be fed with, or replace, fishmeal, actingas colouring agents in such species as salmon, rainbowtrout and koi carp. Improved growth rate and survival, andyolk colour have also been recorded in poultry (Ravishankeret al., 24). Micro-algae have also been fed to ruminantsand pigs. They are a good source of carbohydrates, andsome contain cellulose, usable by ruminants. They tendto be deficient in the sulphur-containing AA, cysteine andmethionine. Other uses listed by the authors include thepresence of bio-active molecules (e.g. phycobiliproteins,polysaccharides) and production of biogas, which can providebio-electricity as an alternative energy source to biofuel.This is an area of great promise waiting for economicallyviable technology to release its potential.ECONOMICSCooper and Weber (1) foresee the future use of agriculturalcrops for biofuel resulting in a small increase in livestockfeed costs, which will be offset to some extent by the useof co-products as feed and by increases in crop yields overtime. Poultry production is a fast growing industry becauseof a rising world demand for animal protein. Feed costsrepresent 65 percent of poultry production costs, whichcould be reduced by largely un-researched co-productssuch as camelina meal, non-toxic jatropha, and detoxifiedjataropha meal (Cherian, 17; Makkar, Kumar and Becker,21). Christensen et al. (26) discuss the difficulty of gettingaccurate data for the costs of wheat DDGS, including thecosts of nutrient management. The authors explain thesensitivity of the industry in North America to the exchangerate between the USA and Canadian dollars, in that astrong Canadian dollar will favour importation of DDGSfrom the USA rather than developing the local industry. Thesame authors also register concern regarding the growth ofthe ethanol industry in Western Canada, where wheat isa major feedstock available in Saskatchewan, whereas thebeef feedlot industry is concentrated in Southern Alberta.Full economic appraisal must include co-products becauseof their influence on pathway selection and economics ofbiofuel production (Wang and Dunn, 27). They suggestthat wet distillers grain may be economically viable withina radius of 80 km of the ethanol plant because savingsin drying costs will offset higher transport costs and a