Posts Tagged ‘Principal Component’
Agriculture – methane, ethanol and biodiesel Introduction
In this chapter we shall discuss the importance of recent developments in agriculture upon the world’s energy resources and the impact on the world population and environment. We shall focus mainly on agriculture producing fuel as this is currently controversial. We will briefly discus the historic link between agriculture and petroleum then we will explore aspects of methane, biodiesel and ethanol production before a brief summary on the strategic importance of a strong agricultural sector.
Link between Agriculture and Petroleum
Since the 1940′s agriculture has dramatically increased its productivity. This is due in part to the use of petrochemical derived pesticides and fertilizers and increased mechanization. The vast majority of energy used to produce food in addition to sunlight comes from fossil fuel sources. Because of modern agriculture’s heavy reliance on petrochemicals there are signs that decreases in oil supply will inflict damage on the world’s modern agricultural system and cause long term food shortages. Oil shortages mean that organic agriculture and sustainable farming are now of more importance than ever. However, the current controversy is due to the fact that farmers have increasingly been raising crops such as corn for non-food use in an effort to help mitigate peak oil. This is turn has contributed to a 60% rise in wheat prices recently and may cause serious social unrest. Increased interest in food commodities from the world’s financial markets has also increased the cost of food worldwide.
Let us look at several main areas of agricultural fuel production. First methane production.
Methane is the principal component of natural gas. The relative abundance of methane and its clean burning process makes it a very attractive fuel. Methane is usually now transported in its natural gas form by pipeline or LNG carriers. Methane is very important for electrical generation when burned as a fuel in a gas turbine or steam boiler and compared to other hydrocarbon fuels burning methane produces less carbon dioxide for each unit of heat released. Methane in the form of compressed natural gas can also be used in vehicles and NASA is looking to methane’s potential as rocket fuel as it is abundant in many parts of the solar system ! In addition methane has industrial uses, especially in industrial chemical processes and may be transported as refrigerated LNG.
The link between agriculture and methane occurs because apart from gas fields an alternative method of obtaining methane is via biogas generated by the fermentation of organic matter, including manure, wastewater sludge, municipal solid waste or any other biodegradable feedstock under anaerobic conditions. As an aside methane hydrates, which are basically icelike combinations of methane and water on the sea floor are also a potential future source of methane. Back to agriculture ! Cattle belch methane accounts for 16% of the world’s annual methane emissions and the livestock sector in general is responsible for 37% of all human influenced methane production. In fact lets take a look at some of the statistics on anthropogenic methane. This accounts in total for approximately 55% of all methane emissions. Of this 18% is due to our energy use, 7% due to landfills, 19% due to livestock, 4% waste treatment, and 7% biomass burning. We can this see the links between agriculture and methane production but of course so far very little of this is harnessed for fuel.
The fermentation of sugar into ethanol is one of the earliest organic reactions known to humanity. Ethanol is also produced from by-products of petroleum refining but here we are concerned at the links between agriculture and fuel production. The largest single use of ethanol is as a motor fuel and fuel additive. The largest national fuel ethanol industries exist in Brazil. Thanks to advances in engine design today almost half of Brazilian cars are able to use 100% ethanol as fuel via ethanol only engines and flex-fuel engines.. In the US flex-fuel engines can run on 0% to 85% ethanol since higher ethanol blends are not allowed. Brazil produces ethanol from domestically grown sugar cane which has a greater concentration of sucrose than corn but is also easier to extract.
In addition the bagasse generated by the process is not wasted but is used in power plants to produce electricity. In contrast in the USA the fuel ethanol industry is based on corn. According to the Renewable Fuels Association in October 2007 there are 131 grain ethanol bio-refineries in the USA with another 72 under construction. The Energy Policy Act of 2005 required that 4 billion gallons of renewable fuel be used in 2006 and this increases thereafter. However there is a controversy arising concerning this as it is disputed whether ethanol as an automotive fuel made from corn results in a net energy gain or loss. The case is clear in sugar cane ethanol as this produces 8 joules for each joule used to produce it. Sugar cane is therefore a far, far better source of ethanol for fuel. Recent research shows that other crops such as switchgrass are also ore efficient than corn. It is likely that cellulosic crops will displace corn as a main fuel crop in the future. There are in fact many controversial side effects of using corn to produce ethanol. According to one estimate a person could be fed for an entire year on the corn used to fill an ethanol fueled SUV. In fact the use of corm almost certainly increases global warming, destroys forests and inflates fuel prices.
Many environmentalists and livestock farmers are against the use of corn for ethanol production and the work also attracts controversial subsidies. In 2007 the UN’s expert on the right to food called for a 5 year moratorium on biofuel production from food crops to prevent a catastrophe for the poor as food prices escalate. The effects of increasing food prices due to the ripple effect of a rise in corm prices have been felt worldwide. A February 2007 Associated Press article stated “The widespread use of ethanol from corn could result in nearly twice the greenhouse gas emissions as the gasoline it would replace because of expected land-use changes”. However, it is not all doom and gloom because as we said earlier the case for ethanol from sugar cane has been made so agriculture has a huge contribution to make to fuel production in an efficient manner in fact if we move away from corn.
This refers to the non-petroleum based diesel fuel made by transesterification of vegetable oils or animal fats, which can be used alone or blended in unmodified diesel engine vehicles. Biodiesel use and production is increasing rapidly and fueling stations are making biodiesel available across Europe and increasingly in Canada and the USA. At the moment biodiesel is relatively expensive to purchase but the economies of scale of production and agricultural subsidies versus the rising costs of petroleum may make biodiesel more attractive. Biodiesel production continues to grow rapidly with an average annual growth rate from 2002 to 2006 of over 40% according to Renewables 2007 Global Status Report. For 2006 total world biodiesel production was 5-6 million tonnes with 4.9 million tonnes processed in Europe – mainly in Germany. It can be seen that agriculture has an enormous role to play in the creation of alternative fuels. A variety of oils can be used to produce biodiesel.
Virgin oil feedstocks such as rapeseed and soybean oils can be used. Soybean is a major feedstock in the US for example. Other feedstocks can include field penny-cress, Jatropha, mustard, flax, sunflower, palm oil, and hemp. Waste vegetable oil (WVO) can also be used as feedstocks. Farms also produce animal fats including tallow, lard and yellow grease. Chicken fats and by-products of the production of Omega 3 fatty acids from fish oil can be used. Another form of farming can also contribute, namely algaculture. Algae which can be grown using waste materials such as sewage can also be used as feedstock.
However, it should be noted that currently worldwide production of vegetable oil and animal fat is not yet sufficient to replace liquid fossil fuel use. Also there would be objections to the vast amount of farming expansion needed to produce sufficient quantities – especially from relative low yield feedstocks like soybean. Lets take a quick look at the various yields because feedstock yield efficiency per acre affects the feasibility of ramping up agriculture required to power a significant percentage of world vehicles.
Here are some examples of yields quoted in US gallons of biodiesel per acre. Algae 1800 gpa or more, Palm oil 508 gpa, Coconut 230 gpa, Rapeseed 102gpa, Soy 59 gpa, Peanut 90 gpa, Sunflower 82 gpa. The case is being made strongly for algae fuel as according to the DOE algae yield 30 times more energy per acre than land crops such as soybeans. Algae production has another great advantage in that it does use up existing farmland. The Jatropha plant is also cited as being relatively high yield with about 200 gpa. This is grown in the Philippines, Mali and India, is drought resistant and can share space with other crops such as coffee. Overall the efficiency and economic arguments continue. Does it make sense to convert more farmland into feedstocks for biodiesel production ?
Additional factors need to be taken into consideration such as the fuel equivalent of energy required for processing, the yield of fuel from raw oil, the return on cultivating food, and effects on food prices and the relative cost of biodiesel versus petrodiesel.
A note on energy security
In reality one of the main drivers for adoption of biodiesel, ethanol and agriculture based methane production is energy security. This means that the country’s dependence on oil should be reduced and substituted with locally available sources such as coal, gas or other renewable resources. In effect this means that there are significant benefits for a country quite apart from reduction of greenhouse gasses. It is clear that initiatives in agriculture to produce methane, biodiesel and ethanol do reduce our dependence on oil , even if the total energy balance is controversial in some cases. The diversification of energy sources is a vital security factor and the development of a strong agricultural sector to meet this demand is therefore of long term and short term strategic interest. However, this must be balanced with initiatives in food production especially in the developing world to offset the effects of conversion of arable land to biofuel feedstock production.
Dr Simon Harding