Tag Archives: biofuel
Biodiesel is often promoted as a clean, green, renewable substitute for regular diesel or petrol. Unfortunately, the green credentials of biodiesel aren’t much better than for ethanol.
|The difference between biodiesel and ethanol
Biodiesel and ethanol are both ‘biofuels‘. However, biodiesel and ethanol are not the same thing. Ethanol is an alcohol made by fermenting sugars. Biodiesel is made from plant oils and animal fats that have been chemically treated with a small amount of methanol.
The problem with biodiesel (and ethanol) is that it is impossible to produce very large amounts of biodiesel without clearing very large amounts of land or converting land used for food production into land used for fuel production. When biodiesel is made from plants grown specifically to produce fuel (and most is), biodiesel is likely to drive up food prices and incur all the attendant problems that go along with land clearing for agriculture – habitat destruction, soil erosion, water quality decline, carbon emissions, etc. Bummer.
On the plus side, biodiesel generates lower emissions of some air pollutants, including hydrocarbons, carbon monoxide and possibly nitrous oxides and particulate matter. Also, we can produce small quantities of biodiesel using waste cooking oil and waste fat from meat production (tallow). And one day soon it may also be possible to produce large quantities of biodiesel on small amounts of land using algae fed from sewage, but as with cellulosic ethanol, the technology for mass production of algae oil is still being developed.
When biodiesel is made from used cooking oil or tallow, overall greenhouse gas emissions are greatly reduced compared to diesel or petrol. However, less than 1% of biodiesel is made this way. Most biodiesel is produced from soybean, sunflower and rapeseed (canola) oil. Other food plant sources include castor beans, coconuts and oil palm – the same plant often blamed for the destruction of orang-utan habitat. When biodiesel is made from crops the overall reduction in greenhouse gas emissions is relatively low and may actually be higher than regular diesel.
So, whether or not you should switch to biodiesel depends on the source of the oil. If the oil comes from old cooking oil or tallow you’ll be reducing your greenhouse gas emissions by up to ninety percent. Fantastic!
However, if your oil comes from sunflower or canola the greenhouse gas reductions are much less. What is worse, you might also be contributing to pushing up food prices and encouraging conversion of land from forest to cropping. That’s bad news for people, forests, orang-utans and carbon emissions. For example, CSIRO in Australia found that biodiesel produced using palm oil grown on cleared forest will produce emissions that are between 8 and 21 times greater than for regular diesel. Ouch!
What is ethanol?
Ethanol is an alcohol fuel usually made by fermenting sugar or starch in wheat, corn, sugar beet, sugar cane and other crops. Yeasts feed on the sugars, creating ethanol and carbon dioxide. The ethanol is then concentrated by distillation. Ethanol is seen by many as a replacement for oil and other fossil fuels because it is a renewable energy supply that can reduce reliance on oil imports.
The (purported) benefits of ethanol
- Lower transport-related carbon emissions: When crops are harvested and ethanol is burned in an engine, CO2 is released into the atmosphere – just as it is when oil and other fossil fuels are burned. The difference with ethanol is that as new crops grow, they absorb CO2 from the atmosphere and the overall concentration of CO2 in the atmosphere stays the same. When fossil fuels are burned, the CO2 stays in the atmosphere and the concentration of CO2 continually increases, contributing to global warming.
- Energy security: Because crops for ethanol can be grown over and over, ethanol has the potential to reduce dependence on oil imports and replace dwindling oil reserves.
Unfortunately, there are some serious drawbacks with ethanol. Some of these are listed below.
10 reasons why ethanol fuel is bad for you and the environment
- Lower fuel efficiency: Ethanol has less energy than gasoline. At higher blend levels (including E85) fuel efficiency will be noticeably lower than for gasoline.
- Agricultural subsidies: Although the price at the pump may seem favourable compared to gasoline, this is partly due to incentives and subsidies paid by governments to farmers, especially in the US and Europe. Not only does this mean that ethanol is effectively subsidised by taxation, the subsidies distort markets and hurt farmers in the third world who can’t compete on the world market.
- Deforestation and habitat destruction: Increasing demand for ethanol crops increases demand for agricultural land. Clearing forests to make more cropland destroys habitat and releases large amounts of carbon into the atmosphere.
- Higher food prices: The land needed to make enough fuel for one car could be used to feed seven people. Ethanol producers buy grain in the same global markets that supply grain for food. Increasing the demand for agricultural land and grain increases the price of food worldwide, and this has a disproportional impact on the poorest people in society.
- Increased use of pesticides: As with most modern farming systems, farmers that grow crops for ethanol rely on pesticides that can contaminate soil, water and air.
- Increased use of artificial fertilisers: To increase yields, farmers use artificial fertilisers made from non-renewable petroleum, natural gas and phosphate minerals.
- Soil erosion and declining water quality: Land clearing and cultivation exposes soil to wind and water erosion. Soil, fertilisers and pesticides are washed into waterways where they can affect ecosystems and contaminate water used for drinking, crops and stock.
- Greenhouse gas emissions: As well as emissions from land clearing and the manufacture of fertilisers and pesticides, there are also emissions from farm machinery. The distilling process also uses a lot of energy. At present much of the energy to distil ethanol comes from coal-fired power stations. The overall reduction in greenhouse gases from using ethanol is relatively small and might sometimes be negative.
- Ethanol can only be a small part of the solution: It takes about ten acres of corn to supply enough fuel for one car. It would take the whole land area of the United States to make enough ethanol to fuel all cars in America today.
- Increased water use: Irrigation to grow crops comes from groundwater or streams and this adds to the overall environmental and social impact of ethanol by reducing water available to ecosystems, food farmers and town drinking water supplies.
So the catch is that ethanol isn’t very good at lowering carbon emissions or improving energy security – but it does cause a lot of problems. In some ways, mining of oil has been replaced with mining of soil and water. And the risk of oil spills has been replaced by the risk of denuded soils, declining water quality and soil fertility. It’s no surprise that ethanol from grains has been called “subsidized food burning”.
Fortunately, it might not be all bad news for ethanol. In this post, we only looked at ethanol from grain and sugar. It might soon be possible to efficiently manufacture ‘cellulosic’ ethanol made from crop residues, wood chips and fast-growing energy crops (like switch grass). If it becomes viable, cellulosic ethanol looks like it might be much more sustainable than ethanol from grain and sugar crops.
Another ‘renewable’ liquid fuel source gaining popularity is biodiesel . Biodiesel is a replacement for normal diesel fuel that is made from vegetable oils or animal fats, including used fats from cooking.
We’ll take a look at both cellulosic ethanol and biodiesel in future posts…
UPDATE: New post – The trouble with biodiesel