Thursday, 12 June 2003

How green is green diesel?

How green is green diesel? Trying to keep abreast of these developments I asked one of the World Land Trust's Trustees, Prof. Renton Righelato to review the issues, and below is a summary he produced - feedback would be very welcome - it's a controversial issue.

Biofuels - a Review by R C Righelato

"Green gasoline", "biofuels" - warm words, an attractive concept perhaps, but just what does it really mean and does it make sense?

Long before Kyoto, governments in many countries had been encouraging the use of biofuels to reduce reliance on imported fossil fuels or as a way of subsidising their farmers. More recently, the threat of global warming has given impetus to the development of "renewables", which are encouraged under the Kyoto Protocol and are planned to replace significant amounts of petroleum over the next decade.

There are many types of biofuels, some created from wastes (particularly methane) others from crops grown for the purpose:
  • vegetable oils from oilseed rape and oil palm added to diesel
  • sugars from maize starch, beet and cane converted by fermentation to ethanol which can be added to petrol
  • plantation forestry or coppicing to produce wood for burning
  • methane from sewage, farm wastes, landfill.
It can only be helpful to make use of wastes, particularly where the potent greenhouse gas, methane, is converted to carbon dioxide, which, carbon for carbon, has a much lower greenhouse effect. But the production of more crops to fill our fuel tanks will only compound the ecological problems we have already created with agriculture, with potentially little or no greenhouse benefit.

This discussion will focus on oilseed rape and biodiesel in the UK, but the same logic applies to bioethanol and to tropical, as well as temperate areas.

UK consumption of diesel in 2002 was 17.6 million tonnes(1). To provide the vegetable oil for this (with present technology, up to 10% vegetable oil, after processing, can be added to diesel), over 1 million hectares of arable land would be required - a massive 25% increase in the total land under crops in the UK and nearly a quadrupling of present oilseed rape production.

The equivalent of 0.56 tonnes of fossil diesel are required to produce 1 tonne of biodiesel (2). So, the use of rapeseed oil for biodiesel gives us an overall saving of fossil fuel of around 4%. Applied to all of the UK's diesel consumption, this represents a saving of 774,000 tonnes of fossil fuel and is equivalent to a saving of carbon released into the atmosphere of around 0.5 tonnes carbon per hectare.

The land needed to supply this quantity of oilseed could come only partly from set-aside and would require further land being brought into cultivation, with a concomitant release of carbon stocks from the soil and ground cover.

If instead, the land were allowed to regenerate as forest over a period of 50 years or so, the rate of removal of carbon from the atmosphere would be around twice as much as the saving arising from the use of biodiesel (3). Sustainably-extracted, such forests could provide timber that, used as a structural material, would increase the carbon "sink" effect in the mature forest.

The ecological cost of intensive, mono-crop agriculture, in terms of lost biodiversity and lost resilience to environmental change is huge. Added to this is the loss of the countryside as an amenity to enjoy and, for many people, the nose, skin and eye irritation that the pollen causes.

A strategy for carbon emissions should firstly be based on using less carbon derived energy – driving more gently and less frequently, more efficient engines etc. Secondly we must develop alternative energy sources out-with the carbon cycle. And thirdly create and maintain stable carbon sinks. This means:
  • protecting established forests and grasslands;
  • re-establishment of stable forests and steppes.

1 DTI Energy Statistics, Government News Network 27 March 2003;

2 Richards IR, 2000 "Energy balances in the growth of oilseed rape for biodiesel and of wheat for bioethanol." British Association for Bio fuels and Oils.

3 Read D et al 2000 "The role of land carbon sinks in the mitigation of global climate change". The Royal Society, London (
Other useful bibliography
DEFRA - Economics and Statistics
Shapouri H, Duffield JA, and Wang M (1998). "The energy balance of corn ethanol". U.S. Department of Agriculture, Office of the Chief Economist, Office of Energy Policy and New Uses. Agricultural Economic Report No. 814.
Shapouri H, Duffield JA, and Graboski MS. (1995) "Estimating the net energy balance of corn ethanol". U.S. Department of Agriculture, Economic Research Service, Office of Energy. Agricultural Economic Report No. 721.

Sheehan J, Camobrecco V, Duffield J, Graboski M, and Shapouri H (1998) "Life cycle inventory of biodiesel and petroleum diesel for use in an urban bus". National Technical Information Service, Springfield VA.

Biofuels - background notes
  • Net Energy Analysis USA : Office of Energy Policy, New Uses (OEPNU)
    US corn to ethanol 1.34
    Soy biodiesel 3.20
  • Net Energy Analysis UK (ref 2)
    UK rapeseed oil 1.78
From DTI statistics:
  • UK transport fuels demand 49Mt/a (2002) of which 17.6Mt DERV
From DEFRA Statistics:
  • Total arable crops in UK 4.5 Mha
  • Rape UK 432 kha; 1.4Mt; £294M
  • Sugar beet 169 kha; 1.4Mt; £272M

1 comment:

  1. check out the documentary called GREEN, it is a powerful account of deforestation in Indonesia to grow palm oil for biodiesel, and the corollary extinction of species. powerful!... and certainly makes you rethink biodiesels