All our petrol and diesel fuels contain a proportion of fuel derived from renewable sources, and there are long term plans to increase the percentage of biofuel in blended fuels. Can this really stave off climate change?
Figures from the UK Department for Transport (1) show that in 20 years from 1990 to 2009 the amount of CO2 emitted by transport was pretty constant at around 122 million tonnes per year. In that time there was a marked decline in emissions from houses and industry as better insulation standards and other energy saving measures came into use.
In the early days of internal combustion engine development there was no consensus on which fuel to use, coal gas was common in stationary engines and early cars often ran on alcohol. The Otto company demonstrated a diesel engine running on groundnut (peanut) oil at the Paris exhibition of 1900. The rise of the petroleum industry in the early part of the 20th century put a stop to all that, cheap petrol and diesel oil made possible mass market motoring and road haulage on the scale we see today. With oil prices rising and the environmental effects of burning fossil fuels better understood biofuels are in the news again.
We have been using some biofuels in our cars, buses and trucks since the 1990s. Ethanol (the type of alcohol found in drinks) was taken up enthusiastically by oil companies because it raises the octane rating of petrol (gasoline). Previously they had used tetraethyl lead which was banned in the early 90s and then methyl tertiary-butyl ether ( MTBE), benzene and toluene. The first caused problems, especially in the US, when leakages contaminated groundwater. The other two are toxic. Ethanol is toxic too but relatively harmless in small quantities.
Most ethanol is produced by fermenting some sugary or starchy plant matter and then distilling the resulting brew. Ethanol contains oxygen so the fuel air mixture entering the engine has to be adjusted, at low ratios this is done automatically by the engine management system of any modern car, for higher ratios ‘flex fuel’ systems can cater for any blend of petrol and ethanol up to 85% ethanol (knowns as E85). Being less energy dense than petrol increases fuel consumption slightly.
Biodiesel derived from oil bearing plants or waste fat from the food industry has some advantages for oil companies too, it is low in sulfur and has higher lubricity (it’s oilier) than conventional diesel fuel.
It has some problems though. In cold weather biodiesel gels at a higher temperature than diesel so blend ratios are normally reduced or extra ‘winterizing’ additives used. A sudden cold spell early in the year when forecourts are still stocking summer grade fuel can be a problem. When Biodiesel blends first started to appear there were reports of clogged fuel systems, this was traced to deposits from conventional diesel in the tank and fuel lines being loosened by the cleaner biodiesel. Mould growth in diesel tanks is quite a common problem, and biodiesel being somewhat more palatable to bugs can make it worse. It isn’t a problem in regularly used vehicles, fuels contain mould inhibitors so regular refuelling keeps the problem at bay. It’s more of an issue for recreational vehicles and boats that may only be topped up once a year, and for fuel storage depots.
Current Consumption Levels
Biofuel use varies a great deal around the world, the EU Renewable Energy Directive (RED) requires the transport sector to use 10% biofuels by 2020, currently most countries are using in the region of 2-5%. The EN590 mineral diesel specification across Europe permits up to 5% biodiesel (B5) so it can be used in any diesel vehicle, at present higher blend ratios should only be used with the vehicle manufacturers approval, though blends right up to B100 are available.
Ethanol too is currently permitted up to 5% in standard lead free petrol (EN228:2008), plans to raise it to 10% at the end of 2013 have been shelved in the UK and elsewhere partly due to scare stories about ethanol damaging engines and fuel systems.
In the US the story is somewhat different, the government mandates how much renewable fuel the oil companies must sell each year. Americans are less inclined to worry about climate change than Europeans, but they are patriotic and concerned about being beholden to foreign powers for their gasoline. A high ethanol mandate has been promoted as a way of reducing dependency on imported oil and good for US farmers whose grain, mainly maize (corn), is the number one feedstock there. Almost overnight a huge ethanol industry sprung up that is wholly dependant on the government mandate. By 2013 40% of the US corn crop was being used to make ethanol.
This year though things are different, domestic production of ‘unconventional’ oil and gas has reduced the level of imports, vehicles have become more efficient slowing the growth in demand for fuel and drivers are wary of higher blend ratios, avoiding them where they are offered. The government’s response has been to reduce the mandate for 2014 from 16.55bn gallons this year to 15.21bn gallons, equivalent to about 10% of the country’s fuel supply. (2)
Further south though things are very different. Brazil has a huge sugar industry, and almost all its sugar is fermented to make ethanol. Standard petrol there is E85, and many forecourts offer E100. Even though the vehicle manufacturers don’t endorse this almost pure ethanol it is popular with motorists because it is cheaper than petrol.
In round figures the total amount of solar radiation reaching the earth’s surface is about 7000 times global energy consumption (3) so you might think it would be easy to grow enough crops to meet all our needs. The problem is existing conversion rates are poor, so it takes a lot of space and time to make a litre of fuel. Green plants convert sunlight to sugar with an efficiency of only around 5%, and to do it they need space to grow, water and a favourable climate. Ethanol is normally made from either starch in grains, or sugar from cane or beet. Biodiesel is normally made from oil bearing fruit and seeds. The rest of the plant, 90% of it or more, is stalks and leaves and roots that are hard to process into liquid fuel. In some cases these waste materials are used as solid fuel increasing the overall efficiency of the process somewhat.
Even at current levels the industry faces accusations that it is driving up the price of food and actually increasing the total level of CO2 emissions by clearing forests and draining swamps to grow more fuel crops. Land Use Change (LUC) is prohibited by RED and similar schemes, but indirect changes (ILUC) are harder to police. If a country converts much of its agricultural land to growing oil palms for Europe then imports more food from a neighbouring country which has increased food production by destroying rain forest, it’s easy to spot what’s happening. In a global market where agricultural products are traded widely it’s almost impossible.
If production is to increase significantly it won’t be by simply growing more corn or oil seed rape in prime farmland.
Biofuels are effective in the narrow technical sense, engines run fine and drivers scarcely notice, but they are less effective in reducing total CO2 emissions. The problem isn’t in the fuel but in the ‘field to forecourt’ processes. Crops need to be grown; fields ploughed, seeds planted, fertilised, irrigated, dosed with pesticides and harvested. The farm machines generally run on diesel and the chemicals are usually made from oil. The crop is transported to a factory usually by truck, the factory needs heat and power and water. In some cases an intermediate product such as palm oil is produced in the country where the crop grows and shipped to Europe or elsewhere for processing into fuel. Biodiesel is commonly made using methanol derived from petroleum. The finished biofuel is then transported to a conventional oil terminal to blend with regular fuel. This maybe local or halfway round the world.
When all this is taken into account more than half the potential reduction in CO2 is often lost, in fact the current RED regulations allow a fuel to be classed as ‘Renewable’ if the makers can demonstrate a 35% saving in CO2 emissions in the whole cycle. A 35% reduction in 5% of the total fuel burn, isn’t a lot. Even if current plans to raise the biofuels requirement to 10% are implemented and the RED definition of ‘renewable’ raised to 50% that will only produce a 5% reduction overall in CO2 emissions from transport.
The objective is to reduce CO2 emissions, biofuels are not the only way of achieving that. All hydrocarbons are made from hydrogen and carbon, ranging from light gasses such as methane that are mostly hydrogen to heavy solids like coal that are mostly carbon. The more carbon you burn the more CO2 you put into the atmosphere. In the US production of natural gas by fracking has reduced its price by about 50%. That has lead to less coal being used in power generation reducing CO2 output. It is possibly to use compressed natural gas (mostly methane) in road vehicles, existing models can be converted and there are moves by manufacturers such as Audi to make gas-fuelled models (4). Until the gas runs out this would reduce CO2 emissions by more that current biofuel technology can, but it’s a short term fix.
Ultimately to have truly sustainable transport we need to produce 100% of our fuel from sunlight, and that has to include all the fuel used in the production process and in distribution. There are many ways this may be achieved, but no obvious leaders at present. One line of enquiry is artificial photosynthesis. Plants have evolved to produce plant matter, and animals have evolved to eat it. For transport we need a liquid or gaseous output. Research focussing on using a catalyst plus sunlight to split water to produce hydrogen has been in progress for years. Other projects intend to output methanol which is similar to ethanol and usable as a liquid fuel, or as an ingredient in biodiesel (5). Both are still a long way from competing with plants.
Over the last 10 years several ‘miracle crops’ have been suggested for biofuel production, things like Jatropha which grows like a weed in S America and yields oil bearing fruit. The snag with all of them is that in order to produce a decent crop they need the same level of inputs as any other plant, and the same amount of agricultural land. Algae are different.
Growing in water algae turn much less of their sugar into the kind of support system that land plants need, and thus a greater proportion is available as sugar or oil. Macro algae (seaweed) can be harvested, dried and fermented to produce ethanol, and some types of micro algae (pond slime) produce oil. Harvesting seaweed on a large scale is not environmentally sustainable, and attempts to grow it on floating platforms have yet to yield sufficient output to justify the cost. Growing algae in ponds looks promising, especially as many can grow in polluted water unsuitable for conventional crops. Space is still an issue, the ponds would have to be big and eat into either agricultural land or wilderness. To increase output in a small space various companies have patented systems that use tanks under glass or transparent plastic, or grow micro algae in vertical plastic tubes. Rather than use farmland these systems are designed to be installed in deserts where there is plenty of sunlight. The technology works but is expensive, so far most companies in this business are focussing on producing high purity oil for pharmaceutical and cosmetic use because it’s more profitable than biodiesel.
Even smaller than micro algae are microbes, and several of them can convert biomass into useful oils and alcohols. The oily film seen on many stagnant ponds is produced by bacteria eating plant matter and excreting oil, unfortunately efforts to scale this up haven’t yet produced commercial quantities. Qteros (6) is a US company that has patented an organism they’ve named the Q Microbe which can consume the woody parts of a plant and produce ethanol. This promises greatly increased yield compared to yeast-based processes that can only use sugars and starches, but they are not producing enough yet to make a difference.
Crystal Ball Gazing
Big industries like oil and gas look for big solutions to their problems, but it seems probable that the business models they operate at the moment will have to change. There is unlikely to be any one miracle crop or process that can replace petroleum, we will have to move toward a very diverse model where local communities make their own fuels using feedstocks and processes that suit their environment, and use as little fuel as possible to grow the fuel crop, process and distribute it.
Since industrialisation took off in the 18th century we have seen transport as essential to a modern society and worked to make it better, cheaper, more available, and faster. Maybe it’s time we started working out how to travel less. Limit the overseas holidays, cut down on sales trips and business meetings. Change employment patterns and planning rules to drastically reduce commuting.
Above all, abolish international climate change conferences in exotic locations. Use Skype!
FOOTNOTES AND FURTHER READING