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7 Biofuels: some of the issues

There are many issues to be considered and weighed up regarding the use of biofuels. The following points will help you to consider further the various implications of using trees, food crops and grasses as fuels.

How does the cost of biofuels compare with that of conventional fuels?

At present, the cost of producing biodiesel and bioethanol is approximately double that for conventional fossil fuels. The UK offers tax incentives to encourage fuel producers to make biofuel and there is also an incentive for consumers: the duty on petrol with 5% biofuel is, at the time of writing (2009), 20 p/litre less than that on ultra-low sulphur petrol.

A recent review has shown that biofuel production is a high-cost process overall; only the production of bioethanol from sugar cane was considered to be cost-effective. If, however, the price of crude oil rises then biofuels may start to become more competitive, although this would depend on fertiliser, and hence biofuel feedstock, prices remaining stable.

Does growing crops for fuel create higher food prices?

One point of view is that using land to grow crops for fuel rather than for food has led to increased food prices, which in turn impacts most on those in developing countries who have to spend a relatively large proportion of their income on food. In 2007, the United Nations Food and Agriculture Organisation (FAO) and the International Food Policy Research Institute (IFPRI) both released reports suggesting that rising food prices were due to the conversion of agricultural land from food to biofuel crops. Subsidies for the biofuel industry, quoted to be in the region of £5.6-6.1 billion per year (FAO), are believed to incentivise farmers to grow biofuel rather than food crops. However, those supporting biofuels hold the view that better production methods, which will use parts of the plant currently wasted in biofuel production, may be able to increase the efficiency of biofuel production.

Does growing biofuel crops result in more fertiliser and pesticide input?

The amount of fertiliser and pesticide input depends on the crop species grown; one criterion for a suitable biomass crop is that it has a low requirement for nutrients. Switch grass, for example, grows well in poor soil conditions and requires around two-thirds less fertiliser input than a food crop such as maize.

Is there a potential loss of biodiversity?

In some cases, the use of biofuels could increase biodiversity (the number of different species found within a given area), for example, by harvesting woodfuel and then replanting with mixed woodlands. Conversely, the increased use of soybeans for biofuel in the USA has caused soybean production to be increased in South America at the expense of Amazonian rainforest, which has been cut down to give more agricultural land. This has the potential to reduce biodiversity. Also, trees in rainforests help absorb CO2 (albeit not at the rate of newly planted forests) and so are believed to play a part in offsetting global warming.

Is the energy output greater than the energy input?

The overall energy balance, that is the net energy output compared to the input needed, is dependent on both the species of biomass crop and the type of biofuel being produced. The inputs to a biofuel crop include both the direct costs of growing, such as fertiliser, cultivation, harvest and labour, and the indirect costs, such as storage of the harvested crops. Processing inputs include pre-treatments, processing for energy release and the removal or reuse of residual waste. Ideal crops are being investigated that require low maintenance, need only low nutrients, grow quickly and can tolerate poor soil conditions. Switch grass is one such plant, and interestingly it has been shown that it is only energy efficient if it is used as a pelleted biomass for fuel rather than for bioethanol production.

Do biofuels reduce carbon emissions?

Burning biofuels does release CO2, but this is CO2 that has been removed from the atmosphere relatively recently, unlike the carbon in fossil fuels which has been removed from the atmosphere for many millions of years. Hence, biomass energy crops are deemed carbon neutral. However, some argue that nitrous oxide, which is 240 times more powerful as a greenhouse gas than CO2, is produced in greater quantities during the production of biogas than during the burning of fossil fuels. Also, biofuel production generates CO2 through the use of agricultural and haulage vehicles for growing and transporting the crop.

Question 22

At the start of this course you were introduced to the terms 'carbon offsetting' and 'carbon neutral'. Now that you have finished reading the course, explain in your own words the difference between the terms 'carbon offsetting' and 'carbon neutral' in the context of biofuels.


When biofuels are grown they take up a certain amount of carbon dioxide from the atmosphere and convert it into stored carbon compounds. When the biofuel is later burnt the carbon in these compounds is converted back into carbon dioxide which is released back into the atmosphere. The amount of carbon dioxide released during combustion is the same as that absorbed during plant growth so on the timescale of years biofuels do not change the amount of carbon dioxide in the atmosphere and so are said to be 'carbon neutral'.

The burning of fossil fuels releases into the atmosphere CO2 that was taken up by plants millions of years ago so increases the total amount of CO2 in the atmosphere. It is possible to calculate the number of new trees that would have to be planted to take up the equivalent amount of CO2 by photosynthesis. Funding the planting of these trees is said to 'offset' the amount of carbon that has been burnt by the use of fossil fuels. For example, when purchasing an airline ticket in 2010, it is possible to offset the carbon cost of the flight by paying for some trees to be planted.

Activity 2

Timing: 45 minutes

Task 1

In this activity you will listen to the audio slidecast in which Dr Angela Karp from Rothamsted Research discusses some of the issues relating to the use of biofuels in the UK.

Dr Angela Karp works at Rothamsted Research International, the largest horticultural research establishment in the UK. Her research group is particularly interested in looking at those plants species that grow well in the UK but which are not used as agricultural crops. They are investigating the ways of optimising how such crops can be utilised for use as liquid biofuels. Listen to the slidecast and then answer the following questions.

(You may find it helpful to listen all the way through once, then read the questions before going back to listen again, pausing where appropriate to make notes.)

Download this video clip.Video player: Video 1
Skip transcript: Video 1

Transcript: Video 1

We are at Rothamsted which is an agricultural research station located just north of London and today we are going to be visiting Dr Angela Karp who is the Director of the Centre for bioenergy and climate change and she is a UK expert on the use of biofuels.
So Angela the work that your group now undertakes here at Rothamsted - can you just outline what that involves and the kind of areas that you're looking at.
Angela Karp
Yes. So what our group essentially is trying to do is to look at how we can use woody crops, non-food crops, foods that aren't used for normal agriculture products, to go into the liquid transport industry.
You can create biofuels from food crops and in some ways it's an easier step in terms of just fermenting the sugars to produce ethanol. But there is obviously a problem with doing that isn't there?
Yeah that's right. These woody plants don't store their sugars in an easy form. They don't store them in the starch or sugar. It's locked up in the cell wall. It's a structural component.
And a cell wall is a very complicated material isn't it? People say just cell wall - it sounds like a brick wall - something very simple. But it's much more complicated than that.
Imagine more, if you like, a fence made of wire netting except you don't have one wire, you have five or six different types of wire, all interlaced. And those wires are locked together. So some of them you can't tease apart from one another very easily because they are locked together by careful bonding.
And the whole idea is to give the plant strength so that it's able to remain upright.
Strength and resistance. The cell wall is actually a very clever structure. But for us it's difficult because it means that we have a complex series of fibres which are all kind of interlaced and locked together. And in order to get the one fibre we want, we have to be able to unlock them and then release just those fibres out of the cell wall. Hence the sugars. And the sugars are in what's called a cellulose or hemicellulose component of the cell wall. And the other components are the lignin I talked about before. Very high calorific value.
That means it's got lots of energy.
Lots of energy. So lignin as a polymer is higher than coal and that's the reason why you can burn these. But for us the lignin is a problem because it's the polymer which gets in the way of getting the sugars. So a lot of the research which is going on is how we can break down the cell wall in a way that releases the sugars and allows us to make the fuel.
So we are starting to screen through the willows and asking, you know, if put through a test where you try to make sugars out of willow, can we identify some which are better at doing that than others. We are also beginning to understand where does the plant put its sugars. It creates sugar by photosynthesis and can we understand how it makes the cell wall from those sugars. Can we try to select plants which make the cell wall in a way that's more easy to break down. So it's still resistant, it still keeps off water but it's easier for us to break it down.
End transcript: Video 1
Video 1
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Question 1

  1. What type of research is Angela Karp's group doing?
  2. What are the main difficulties in using woody crops as biofuels?
  3. Which polymers within the cell wall contain the sugars? What other component of the cell wall makes it particularly difficult to access the sugar-containing polymers?
  1. It is investigating woody crops (i.e. non-food crops) to see what their potential is for using as liquid transport biofuels. She is particularly interested in using different types of willow trees and researching how they use the sugar from photosynthesis to produce cell walls.
  2. The sugars contained within woody crops are locked away as components of the plant cell wall and this can make them difficult to access and to liberate.
  3. Both cellulose and hemicellulose (which is another type of cellulose) are polymers containing sugars (these sugars are composed of glucose monomers. Lignin is the polymer that made it difficult to access the sugar-containing polymers.

If you would like to know how Angela Karp became interested in plants, you can listen to another short audio clip.

Download this audio clip.Audio player: Audio 3
Skip transcript: Audio 3

Transcript: Audio 3

So Angela, could you recall your first memory of plants and how you became interested in them?
Angela Karp
Well interestingly I did do plants at school but I didn't go to do plants at university. I went to do work on animals because I've always been very interested in animals. But in my first year of university, for the first time I really understood genetics. I just did not get it at school. And I think because of that I then became very fascinated by what one could do with genetics and it was much easier to experiment with plants than animals. So at that point I shifted my attention to plants, became much more interested in plants and crops and the importance of food and agriculture. And I went along that path.
And who fired your enthusiasm then in terms of the genetics and allowing you to understand it?
I think I just had a really good lecturer. I was at London University Queen Mary College and I had a really good lecturer in genetics and he just inspired me. And I think most importantly I understood the concept which I just hadn't got at school. But I did well in my A level biology but I just hadn't got the concept. And suddenly understood it and I think with that comprehension I became very interested in how we could apply it, particularly for agriculture.
And often that's the way. You just need that one person to fire your enthusiasm and you're off then. So was your degree actually in plant science?
Actually, no. So what happened was I was at university in London and they did a lot of course units. And it ended up that I had so many course units in genetics - so I did for example developmental genetics, fungal genetics, all in genetics - that I actually ended up with a BSc in genetics. And I was one of the few people who graduated with a BSc in genetics. Most people came out with Biological Sciences, which is much more typical.
More general in many ways.
That's right.
So that's the kind of area that you are still working in. So how did your career progress from that point onwards?
Well I went on to do a PhD and at the time there were not that many places that offered PhDs in agricultural sciences and agricultural departments were quite few. So Reading, for example, Aberystwyth - there was a few in the country. I was fortunate to get a good PhD in Aberystwyth, which is one of those well-known departments. And again they had a very strong genetics slant in the way they worked so that suited my sort of interest, if you like. So I did my PhD in Wales and that gave me a break from London so it was quite a contrast - extreme contrast from being in a city to Wales. And then I was fortunate to see the position offered here at Rothamsted. And I went for that and you know I was very fortunate to get that straight out of my PhD.
Because normally people have to spend a little bit more time doing post-doctoral research or whatever before they are able to get a position like that.
That's right. Normally have two posts. But I was fortunate because they were specifically looking for somebody who was a geneticist and who could apply genetics to agriculture. So I guess I was just lucky that opening came up at the time when I was finishing my PhD.
So when did you come to Rothamsted?
In 1981 so I've been in the Institute for all that time.
End transcript: Audio 3
Audio 3
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