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Livestock, Climate Change and the Environment
Responding to the challenges posed by global warming, peak oil and biofuels will require a paradigm shift in the practice of agriculture and in the role of live stock within the farming system. Farming systems should aim at maximizing plant biomass production from locally available diversified resources, processing of the biomass on farm to provide food, feed and energy and recycling of all waste materials.
The approach that is the subject of this paper is that the generation of electricity can be a by-product of food/feed production. The concept is the fractionation of biomass into inedible cell wall material that can be converted to an inflammable gas by gasification, the gas in turn being the source of fuel for internal combustion engines driving electrical generators. The cell contents and related structures such as tree leaves are used as human food or animal feed. As well as providing food and feed the model is highly appropriate for decentralized small scale production of electricity in rural areas. It also offers opportunities for sequestration of carbon in the form of biochar, the solid residue remaining after gasification of the biomass.
The components of the world crises – economic recession, global warming and resource depletion (especially fossil fuels) - presently facing humanity are closely inter-related. The gaseous emissions from the burning of fossil fuels are the major contributor to global warming; the apparently inexhaustible supply of fossil fuels facilitated the exponential growth of the world population during the past century and, more recently, the unsustainable indebtedness in the developed countries, which led to the economic recession of 2008-09.
In the past century, the needs for energy, and indirectly for food, of the expanding world population were provided by cheap oil. The inevitable process of adaptation to increasing cost and declining supplies of oil, will almost certainly change the future life style of the majority of the world’s population. On the positive side it will provide greater opportunities for small scale farmers as there will be comparative advantages - economic, social and environmental - for the utilization of biomass for food, feed and fuel production, in a world in the decline phase of the oil age. This is because over 70% of fossil fuel is used for transport. As the supply diminishes and the price increases, transport will be the sector most affected. Most forms of biomass are of low bulk density. Thus, there will also be comparative advantages for decentralization and localization of both production and processing of this resource.
For the future, the only long term alternative to fossil fuel (as exosomatic energy - that is energy not derived from digested food – muscle power) is solar energy, utilized either directly as a source of heat, or indirectly in solar-voltaic panels, as wind, movements of waves and tides, or in biomass produced by photosynthesis. Solar energy will also have to be relied on to produce food, in what must surely have to be small-farm systems in rural areas, to support the largely urbanized population, The green revolution which dramatically increased food supplies during the last 40 years was a “fossil energy “ revolution as it was energy in the form of oil and natural gas which facilitated production of fertilizers, especially nitrogen, pesticides and herbicides, and the mechanization and irrigation that permitted multiple cropping.
There are few difficult decisions about producing food by photosynthesis. By contrast, the ideas proposed for redirecting energy from the sun into potential energy to replace that of fossil fuels are many. Rapier (2009) describes many of these proposals as Renewable Fuel Pretenders arguing that their proponents believe they have a solution but that it will never develop into a feasible technology because the proponents “have no experience at scaling up technologies”. In this category he lists cellulosic ethanol, hydrogen and diesel oil from algae.
It is surprising that gasification of biomass, as a means of producing a combustible gas, has received so little attention – perhaps because it is not a new technology. It is one of the purposes of this thesis to demonstrate that it holds real prospects of being applicable at the small, dispersed farm level, provided it is developed as a component of a mixed, integrated farming system.
Gasification is a process for deriving a combustible gas by burning fibrous biomass in a restricted current of air. The process is a combination of partial oxidation of the biomass with the production of carbon which at a high temperature (600-800 °C) acts as a reducing agent to break down water and carbon dioxide (from the air) to hydrogen and carbon monoxide, both of which are combustible gases. The by-products of the process are biochar (a mixture of minerals and carbon) and tar (Rodríguez and Preston 2010). Biochar has enormous potential as a soil conditioner and a sink for atmospheric carbon (Rodríguez and Preston 2009) while the tar is an important element in the construction and maintenance of roads.
The advantages of gasification are that: the feedstock is the fibrous parts of plants which are not viable sources of food or feed; the energy used to drive the process is derived from the combustion of the feedstock; there is minimal input of fossil fuel (mainly for the construction of the gasifier and associated machinery); and the process can be de-centralized as units can be constructed with capacities between 4 and 500KW.
Several writers (eg; Brown 2007 and Falvey 2008) have challenged the morality of converting food into liquid fuel, in a world where one third of the population is already mall-nourished with certain prospects that this proportion will increase as the world population marches on to the 8 to 9 billion predicted before the mid-point of this century. Second generation ethanol from cellulosic biomass is also not the answer, as apart from the doubtful economics of the process, the major proposed feedstocks – Switch grass and Miscanthus – provide no food component.
As indicated earlier, this conflict can be avoided by using gasification to produce the fuel energy, as the feedstock can be the cellulosic component of the plant, leaving the more digestible protein and carbohydrate components as the source of food/feed. The most useful end products of gasification are electricity and biochar, thus electrification of most road transport systems is a necessary corollary. Utilization of biochar will be facilitated by locating the gasification process within the farm producing the biomass.
The choice of sugar cane as the pivotal crop in the farming system is justified by it's high yield and efficient use of solar energy, and the ease of separating the 100% digestible sugar cane juice from the structural fibre (bagassse). Because the juice contains no fibre, it is the perfect medium for facilitating the incorporation in diets for pigs of protein-rich vegetative sources such as the edible leaves of trees, shrubs and vegetables, the levels of which in cereal-based diets are constrained by their moderately high levels of fibre. Research has been done with several protein-rich forages, including the leaves of cassava and mulberry, the vines of sweet potato, the leaves and stems of water spinach and more recently the leaves and stems of Taro, Cocoyam and New Cocoyam (Preston 2006). Chhay Ty et al (2009) recently reviewed the research done with these different forages and came to the conclusion that the Colocacia, Alocacia and Xanthosoma members of the Araceae family offered the greatest potential as vegetative protein sources in pig diets because of their high yield, ease of cultivation (many species grow wild in ponds and in the forests (Peng Buntha et al 2008; Ngo Huu Toan and Preston 2007), ease of conservation by ensiling, and the apparent relatively high energy value of the stems complementing the protein in the leaves.
The choice of pigs as the main live stock component in an integrated farming system is justified by several factors: ease of marketing the meat, low investment (compared with cattle), and the fact that pig excreta is the preferred feedstock in anaerobic biodigesters http://www.fao.org/WAICENT/FAOINFO/AGRICULT/AGA/AGAP/FRG/recycle/default.htm.
The advantages offered by sugar cane as a combined source of feed for pigs and gasifier feedstock have already been discussed. A similar synergism applies to the use of forage trees as the protein source for goats. The browsing habit of this species facilitates the separation of the leaves, which become the protein component of the diet, while the residual stems are easily processed as feedstock for the gasifier.
In the TOSOLY farming system, the chosen trees species are Mulberry (Morus alba) and Tithonia (Tithonia diversifolia). Mulberry leaves have been extensively studied as a protein source for ruminants, mainly goats (Yao et al 2000; Theng Kouch et al 2003; Nguyen Xuan Ba et al 2005; Pathoummalangsy Khamparn and Preston 2008; KhamphoumeSouksamlane et al 2009). The conclusion of KhamphoumeSouksamlane et al (2009) was that Mulberry leaves almost certainly were rich in “bypass” protein in view of the marked increases they induced in the growth rate of goats.
The multi-purpose role of sugar cane is apparent in the fact that for pig feeding and gasification, only the stalk is used. The growing point and leaves are thus available as a potential energy-feed resource for ruminants.
In a recent paper, on the "Post Carbon Institute" web site, Heinberg and Bomford (2009) stated that "The only way to avert a food crisis resulting from oil and natural gas price hikes and supply disruptions while also reversing agriculture’s contribution to climate change is to proactively and methodically remove fossil fuels from the food system". Their proposals in relation to farming systems were that:
"Farmers should move toward regenerative fertility systems that build humus and sequester carbon in soils, thus contributing to solving climate change rather than exacerbating it.
More of the renewable energy that will power society can and must be generated on farms. Wind and biomass production, in particular, can provide farmers with added income while also powering farm operations".
In the same report they referred to papers indicating that, compared with large farms, "smaller farms have greater biodiversity (Hole et al 2005), more emphasis on soil-building (D’Souza and Ikerd 1996) and greater land-use efficiency (Rossett 1999).
In a review of the investment opportunities in agriculture to increase food production in a resource-depleted world (Kahn and Zaks 2009), the point was made that "Alternative approaches are being researched and tested in development such as the reemergence of small, self-sufficient organic farms, characterized as local, multi-crop, energy and water efficient, low-carbon, socially just, and self-sustaining".
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