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ISIS Press Release 12/12/07
Saving and Restoring Forests Saves Far More Carbon Emissions
than Biofuels
Biofuels out forests in, scientists advise policy-makers to concentrate
on increasing fuel efficiency in the short term and restoring unused croplands
to forests. Selective harvesting of wood waste and biomass from standing forests may
be sustainable. Dr. Mae-Wan Ho
Biofuels have been widely
and mistakenly promoted for mitigating carbon missions as fossil energy is
at or past its peak [1] (Biofuels: Biodevastation,
Hunger & False Carbon Credits, SiS 33). Many critics have pointed out that
biofuels compete for land that should be growing food, and furthermore, they
give poor, even negative energy returns when proper lifecycle accounting is
done [2] (Biofuels for Oil Addicts,
SiS 30). More importantly, bioenergy
crops are a strong driver of deforestation, which results in net release of
huge amounts of CO2.
Rento Righelato
of the World Land Trust, Suffolk, and Dominick V Spracklen at University of
Leeds in the UK have compared the carbon mitigation potentials of various
biofuels with other uses of the land required for growing the bioenergy crop
[3]. As land is the limiting resource, they argue, the appropriate basis for
comparison is the amount of C saved per hectare a year. A period of 30 years
is used for comparison, which seems reasonable, as it takes time for bioenergy
crop plantations to mature and for carbon stocks of cut forests to turn into
carbon dioxide. Moreover, it would take that much time for ‘carbon-free’ fuel
technology to be widely available.
Their results are
summarised in Figure 1 (redrawn from [3]).
Figure 1. Carbon saved on different options
They have made
no allowance for emissions arising from change in land use to produce the
bioenergy crop. As can be seen, planting a forest in the same area of land
would sequester two to nine times more carbon over a 30-year period than the
emissions avoided by using biofuels.
Furthermore,
large areas of land are needed to make significant quantities of biofuels.
A 2004 report from the International Energy Authority [4] estimated that 10
percent substitution of fossil fuels would require 43 percent and 38 percent
of current cropland area in the United States and Europe respectively.
That means forests and grasslands would need to be cleared even at this low
level of substitution. Clearing would result in the rapid release of carbon
stores in the vegetation and the soil that would outweigh any avoided emissions.
The most disastrous
option is to convert tropical forest into cropland, which results in a net
loss (emission) of 200 t C/ha.
The Stern Report on the economics of climate change [5] commissioned by the
UK Treasury noted that putting a stop to deforestation is by far the most
cost-effective way to mitigate climate change, for as little as $1/t CO2 [6]
(see The Economics
of Climate Change, SiS 33).
Righeleto and
Spracklen point out that of the options for biofuels, only conversion of woody
biomnass may be compatible with retention of forest carbon stocks, especially
if it means making use of wood wastes and harvesting appropriately from standing
forests. This would involve selective felling of the biggest trees, which
has been shown to encourage the most carbon assimilation in new growth and
result in the greatest benefit for biodiversity [7] (Multiple Uses of Forests, SiS 26).
If the prime
object of the policies on biofuels is mitigating carbon emissions, Rigehleto
and Spracklen note: “policy-makers may be better advised in the short term
(30 years or so) to focus on increasing the efficiency of fossil fuel use,
to conserve the existing forests and savannahs, and to restore natural forest
and grassland habitats on cropland that is not needed for food.”
Apart from reducing net CO2 emissions, conversion of large areas
of land back to secondary forest provides other environmental services, such
as prevention of desertification and maintenance of regional climate regulation
[8] (see Greening the
Desert, How Farmers in Sahel Confound Scientists, SiS 37), providing
forest products, maintenance of biodiversity.
The only ‘biofuel’
that is truly sustainable is methane from anaerobic digestion of biological
and livestock wastes [9, 10] (see Biogas China, SiS 32; Biogas Bonanza for Third World
Development , SiS 27).
References
- Ho
MW. Biofuels: biodevastation, hunger false carbon credits. Science in Society 33, 36-39, 2007.
- Ho MW. Biofuels for
oil addicts. Cure worse than the addiction? Science in Society 30,
29-30, 2006.
- Righelato R and Spracklen
DV. Carbon mitigation by biofuels or by saving and restoring forests? Science
2007, 317, 902.
- International Energy
Authority, Biofuels for Transport: An International Perspective, IEA, Paris,
2004. http://www.iea.org/textbase/nppdf/free/2004/ biofuels2004.pdf
- Stern Review on the Economics of Climate Change, HM Treasury,
2007, http://www.hm-treasury.gov.uk/independent_reviews/stern_review_economics_climate_change/stern_review_report.cfm
- Saunders PT. The economics
of climate change. Science in Society 33,
20-23, 2007.
- Ho MW. Multiple uses
of forests. Science
in Society 26, 18-19, 2005.
- Ho MW and Lim LC. Greening the desert, how farmers in Sahel confound scientists.
Science in Society 37
(to appear).
- Li K-H, and Ho MW.
Biogas China. Science in Society 32,
34-37, 2006.
- Ho MW. Biogas bonanza
for Third World Development Science in Society 27,
29, 2005.
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