ISIS Report 31/1/08
Mitigating Climate Change through Organic Agriculture and Localized
Organic, sustainable agriculture that localize food systems has the potential
to mitigate nearly thirty percent of global greenhouse gas emissions and save
one-sixth of global energy use. Dr.
Mae-Wan Ho and Lim Li Ching
referenced a version of this article is posted on ISIS members’ website and is available for download here
agriculture of the “Green Revolution” contributes a great deal to climate
change. It is the
main source of the potent greenhouse gases nitrous oxide and methane; it is
heavily dependent on the use of fossil fuels, and contributes to the loss
of soil carbon to the atmosphere  (Feeding the World under Climate Change,
SiS 24), especially through deforestation to make more land available
for crops and plantations. Deforestation is predicted to accelerate as bio-energy
crops are competing for land with food crops  (Biofuels: Biodevastation,
Hunger & False Carbon Credits,
SiS 33). But what makes our
food system really unsustainable is the predominance of the globalised commodity
trade that has resulted in the integration of the food supply chain and its
concentration in the hands of a few transnational corporations. This greatly
increases the carbon footprint and energy intensity of our food consumption,
and at tremendous social and other environmental costs. A UK government report
on food miles estimated the direct social, environmental, and
economic costs of food transport at over £9 billion each year, which is 34
percent of the £26.2 billion food and drinks market in the UK  (Food Miles and Sustainability, SiS 28).
Consequently, there is much scope for mitigating climate change and
reversing the damages through making agriculture and the food system as a
whole sustainable, and this is corroborated by substantial scientific and
empirical evidence (see below). It is therefore rather astonishing
that the Intergovernmental Panel on Climate Change should fail to mention
organic agriculture as a means of mitigating climate change in its latest
2007 report ; nor does it mention localising food systems and reducing
long distance food transport .
Reducing direct and indirect energy use in agriculture
There is no
doubt that organic, sustainable agricultural practices can provide
synergistic benefits that include mitigating climate change. As stated in the 2002 report of the United
Nations Food and Agriculture Organisation (FAO), organic agriculture enables
ecosystems to better adjust to the effects of climate change and has major
potential for reducing agricultural greenhouse gas emissions .
The FAO report found that,
“Organic agriculture performs better than conventional agriculture on a per
hectare scale, both with respect to direct energy consumption (fuel and oil)
and indirect consumption (synthetic fertilizers and pesticides)”, with high
efficiency of energy use.
Since 1999, the Rodale Institute’s long-term trials in the United
States have reported that energy use in the conventional system was 200 percent
higher than in either of two organic systems - one with animal manure and
green manure, the other with green manure only - with very little differences
in yields . Research in Finland showed that while organic farming used
more machine hours than conventional farming, total energy consumption was
still lowest in organic systems ; that was because in conventional systems,
more than half of total energy consumed in rye production was spent on the
manufacture of pesticides.
Organic agriculture was more energy efficient than conventional agriculture
in apple production systems [9, 10]. Studies in Denmark compared organic and
conventional farming for milk and barley grain production . The energy
used per kilogram of milk produced was lower in the organic than in the conventional
dairy farm, and it also took 35 percent less energy to grow a hectare of organic
spring barley than conventional spring barley. However, organic yield was
lower, so energy used per kg barley was only marginally less for the organic
than for the conventional.
The total energy used in agriculture accounts for about
2.7 percent of UK’s national energy use , and about 1.8 percent of national
greenhouse gas emissions  based on figures for 2002, the latest year for
which estimates are available. Most of the energy input (76.2 percent) is
indirect, and comes from the energy spent to manufacture and transport fertilizers,
pesticides, farm machinery, animal feed and drugs. The remaining 23.8 percent
is used directly on the farm for driving tractors and combine harvesters,
crop drying, heating and lighting glasshouses, heating and ventilating factory
farms for pigs and chickens. Nitrogen fertiliser is the single most energy
intensive input, accounting for 53.7 percent of the total energy use. Thus,
phasing out nitrogen fertilizer will save 1.5 percent of national energy use
and one percent of national ghg emissions, not counting the nitrous oxide
from N fertilizers applied to the fields (see below). Globally, the savings
in fossil energy use and ghg emissions could easily be double these figures.
It takes 35.3 MJ of energy on average to produce each
kg of N in fertilizers . UK farmers use about 1 million tonnes of N fertilisers
each year. Organic farming is more energy efficient mainly because it does
not use chemical fertilizers .
The Soil Association found that organic farming in the UK is overall
about 26 percent more efficient in energy use per tonne of produce than conventional
farming, excluding tomatoes grown in heated greenhouses . The savings
differ for different crops and sectors, being the greatest in the milk and
beef, which use respectively 28 and 41 percent less energy than their conventional
Amid rapidly rising
oil prices in 2006, with farmers across the country deeply worried over the
consequent increase in their production costs, David Pimentel at Cornell University,
New York, in the United States returned to his favourite theme : organic
agriculture can reduce farmers’ dependence on energy and increase the efficiency
of energy use per unit of production, basing his analysis on new data.
On farms throughout
the developed world, considerable fossil energy is invested in agricultural
production. On average in the US, about 2 units of fossil fuel energy is invested
to harvest a unit of energy in crop. That means the US uses more than twice
the amount of fossil energy than the solar energy captured by all the plants,
which is ultimately why its agriculture cannot possibly sustain anything like
the biofuel production promoted by George W. Bush  (Biofuels for Oil Addicts, SiS 30).
Corn is a high-yield
crop and delivers more kilocalories of energy in the harvested grain per kilocalorie
of fossil energy invested than any other major crop . `
Counting all energy inputs in fossil fuel equivalents
in an organic corn system, the output over input ratio was 5.79 (i.e., you
get 5.79 units of corn energy for every unit of energy you spent), compared
to 3.99 in the conventional system. The organic
system collected 180 percent more solar energy than the conventional. There
was also a total energy input reduction of 31 percent, or 64 gallons fossil
fuel saving per hectare. If 10 percent of all US corn were grown organically,
the nation would save approximately 200 million gallons of oil equivalents.
Organic soybean yielded 3.84 kilocalories of food energy per kilo of fossil
energy invested, compared to 3.19 in the conventional system and the energy
input was 17 percent lower. Organic beef grass-fed system required 50 percent
less fossil fuel energy than conventional grain-fed beef.
Lower greenhouse gas emissions
Globally, agriculture is
estimated to contribute directly 11 percent to total greenhouse gas emissions
(2005 figures from Intergovernmental Panel on Climate Change) . The total
emissions were 6.1Gt CO2e, made up almost entirely of CH4
(3.3 Gt ) and N2O (2.8Gt). The contributions will differ from one country to another, especially between
countries in the industrial North compared with countries whose economies
are predominantly agricultural.
In the United States, agriculture contributes 7.4 percent
of the national greenhouse gas emissions . Livestock enteric fermentation
and manure management account for 21 percent and 8 percent respectively of
the national methane emissions. Agricultural soil management, such as fertilizer
application and other cropping practices, accounts for 78 percent of the nitrous
In the UK, agriculture is estimated to contribute directly
7.4 percent to the nation’s greenhouse gas emissions, with fertilizer manufacture
contributing a further 1 percent , and is comprised entirely of methane
at 37.5 percent of national total  and nitrous oxide at around 95 percent
of the national total . Enteric fermentation is responsible for 86 percent
of the methane contribution from agriculture, the rest from manure; while nitrous
oxide emissions are dominated by synthetic fertilizer application (28 percent)
and leaching of fertilizer nitrogen and applied animal manures to ground and
surface water (27 percent) .
Assuming half of all nitrous oxide emissions come from N fertilizers,
phasing them out would save 11.56 Mt of CO2e. This is equivalent
to another 1.5 percent of the national ghg emissions. The total ghg savings
from phasing out N fertilizers amount to 2.5 percent of UK’s national emissions.
The UK is not a prolific user of N fertilizers compared to other countries,
so globally, it seems reasonable to estimate that phasing out N fertilizers
could save at least 5 percent of the world’s ghg emissions. This is consistent
with earlier predictions.
The FAO had already estimated that organic
agriculture is likely to emit less nitrous oxide (N2O) . This is due to lower N inputs, less N from organic
manure from lower livestock densities; higher C/N ratios of applied organic
manure giving less readily available mineral N in the soil as a source of
denitrification; and efficient uptake of mobile N in soils by using cover
Greenhouse gas emissions
were calculated to be 48-66 percent lower per hectare in organic farming systems
in Europe , and were attributed to no input of chemical N fertilizers,
less use of high energy consuming feedstuffs, low input of P, K mineral fertilizers,
and elimination of pesticides, as characteristic of organic agriculture.
Many experiments have found reduced leaching of nitrates from organic soils
into ground and surface waters, which are a major source of nitrous oxide (see
above). A study reported in 2006 also found reduced emissions of nitrous oxide
from soils after fertilizer application in the fall, and more active denitrifying
in organic soils, which turns nitrates into benign N2 instead of
nitrous oxide and other nitrogen oxides  (see Cleaner
Healthier Environment for All, SiS 37).
It is also possible that moving away from a grain-fed to a predominantly grass-fed
organic diet may reduce the level of methane generated, although this has yet
to be empirically tested. Mike Abberton, a scientist at the Institute of Grassland
and Environmental Research in Aberystwyth, has pointed to rye grass bred to
have high sugar levels, white clover and birdsfoot trefoil as alternative diets
for livestock that could reduce the quantity of methane produced .
A study in New Zealand had
suggested that methane output of sheep on the changed diet could be 50 percent
lower. The small UK study did not achieve this level of reduction, but found
nevertheless that “significant quantities” of methane could be prevented
from getting into the atmosphere. Growing clover and birdfoot trefoil could
help naturally fix nitrogen in organic soil as well as reduce livestock methane.
Greater carbon sequestration
Soils are an
important sink for atmospheric CO2, but this sink has been increasingly depleted by conventional
agricultural land use, and especially by turning tropical forests into agricultural
land. The Stern Review on the Economics of Climate Change commissioned by
the UK Treasury and published in 2007  highlights the fact that 18 percent
of the global greenhouse gas emissions (2000 estimate) comes from deforestation,
and 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 
(see The Economics
of Climate Change, SiS 33).
There is also much scope for converting existing plantations to sustainable
agroforestry and to encourage the best harvesting practices and multiple uses
of forest plantations [29, 30] (Multiple
Uses of Forests, Sustainable
Multi-cultures for Asia & Europe, SiS 26)
Sustainable agriculture helps to counteract climate change by restoring
soil organic matter content as well as reducing soil erosion and improving
soil physical structure. Organic soils also have better water-holding capacity,
which explains why organic production is much more resistant to climate extremes
such as droughts and floods  (Organic Agriculture Enters Mainstream,
Organic Yields on Par with Conventional
& Ahead during Drought Years, SiS 28), and water
conservation and management through agriculture will be an increasingly important
part of mitigating climate change.
The evidence for increased carbon sequestration in organic soils
seems clear. Organic matter is restored through the addition of manures, compost, mulches and cover crops.
Agriculture Farming Systems (SAFS) Project at University of California Davis
in the United States  found that organic carbon content of the soil increased
in both organic and low-input systems compared with conventional systems,
with larger pools of stored nutrients. Similarly, a study of 20 commercial
farms in California found that organic fields had 28 percent more organic
carbon . This was also true in the Rodale Institute trials, where soil
carbon levels had increased in the two organic systems after 15 years, but
not in the conventional system . After 22 years, the organic farming systems
averaged 30 percent higher in organic matter in the soil than the conventional
In the longest running agricultural trials on record of more than 160 years,
the Broadbalk experiment at Rothamsted Experimental Station, manure-fertilized
farming systems were compared with chemical-fertilized farming systems .
The manure fertilized systems of oat and forage maize consistently out yielded
all the chemically fertilized systems. Soil organic carbon showed an impressive
increase from a baseline of just over 0.1 percent N (a marker for organic
carbon) at the start of the experiment in 1843 to more than double at 0.28
percent in 2000; whereas those in the unfertilized or chemical-fertilized
plots had hardly changed in the same period. There was also more than double
the microbial biomass in the manure-fertilized soil compared with the chemical-fertilized
It is estimated that up to 4 tonnes CO2 could be sequestered
per hectare of organic soils each year . On this basis, a fully organic
UK could save 68 Mt of CO2 or 10.35 percent of its ghg emissions
each year. Similarly, if the United States were to convert all its 65 million
hectares of crop lands to organic, it would save 260 Mt CO2 a year
. Globally, with 1.5335 billion hectares of crop land  fully organic,
an estimated 6.134 Gt of CO2 could be sequestered each year, equivalent
to more than 11 percent of the global emissions, or the entire share due to
As Pimentel stated : “..high level of soil organic matter in
organic systems is directly related to the high energy efficiencies observed
in organic farming systems; organic matter improves water infiltration and
thus reduces soil erosion from surface runoff, and it also diversifies soil-food
webs and helps cycle more nitrogen from biological sources within the soil.”
Reducing energy and greenhouse gas emissions in localised sustainable food
Agriculture accounts only
for a small fraction of the energy consumption and greenhouse gas emissions
of the entire food system.
Pimentel  estimated
that the US food system uses about 19 percent of the nation’s total fossil
fuel energy, 7 percent for farm production, 7 percent for processing and packaging
and 5 percent for distribution and preparation. This is already an underestimate,
as it does not include energy embodied in buildings and infrastructure, energy
in food wasted, nor in treating food wastes and processing and packaging waste,
which would be necessary in a full life cycle accounting.
Similarly, when the emissions from the transport, distribution, storage, and
processing of food are added on, the UK food system is responsible for at least
18.4 percent of the national greenhouse gas emissions , again, not counting
buildings and infrastructure involved in food distribution, nor wastes and waste
Here’s an estimate of the greenhouse gas emissions from eating based on a full
life cycle accounting, from farm to plate to waste, from data supplied by CITEPA
(Centre Interprofessionnel Technique d’Eudes de la Pollution Atmosphérique)
for France .
|Greenhouse gas emissions from eating (France)|
|Agriculture direct emissions||42.0 Mt C|
|Fertilizers (French fertilizer industry only, more than half imported.)||0.8 Mt C |
|Road transport goods (within France only, not counting export/import)||4.0 Mt C|
|Road transport people||1.0 Mt C|
|Truck manufacture & diesel||0.8 Mt C|
|Store heating (20% national total)||0.4 Mt C|
|Electricity (nuclear energy in France, multiply by 5 elsewhere)||0.7 Mt C|
|Packaging||1.5 Mt C|
|End of life of packaging (overall emissions of waste 4 Mt)||1.0 Mt C|
|Total||52.0 Mt C|
|National French emission||171.0 MtC|
|Share linked to food system||30.4%|
The figure of 30.4
percent is still an underestimate, because it leaves out emissions from the
fertilizers imported, from pesticides, and transport associated with import/export
of food. Also, the emission of electricity from established nuclear power stations in France
is one-fifth of typical non-nuclear sources. Others may argue that one needs
to include infrastructure costs, so that buildings and roads, as well as the
building of nuclear power stations need to be accounted for.
On the most conservative
estimates based on these examples, localising food systems could save at least
10 percent of CO2 emissions and 10 percent of energy use globally.
The tale of a bottle of ketchup
It is estimated that food
manufacturing is responsible for 2.2 percent and packaging for 0.9 percent
of UK’s ghg emissions , while in the US, 7 percent of the nation’s energy
use goes into food processing and packaging.
A hint of how food
processing and packaging contribute to the energy and greenhouse gas budgets
of the food system can be gleaned by the life-cycle analysis of a typical
bottle of ketchup.
The Swedish Institute for Food and Biotechnology did
a life-cycle analysis of tomato ketchup, to work out the energy efficiency
and impacts, including the environmental effects of global warming, ozone
depletion, acidification, eutrophication, photo-oxidant formation, human toxicity
and ecotoxicity .
studied is one of the most common brands of tomato ketchup sold in Sweden,
marketed in 1 kg red plastic bottles. Tomato is cultivated and processed into
tomato paste in Italy, packaged and transported to Sweden with other ingredients
to make tomato ketchup.
bags used to package the tomato paste were produced in the Netherlands and
transported to Italy; the bagged tomato paste was placed in steel barrels,
and moved to Sweden. The five-layered red bottles were either made in the
UK or Sweden with materials from Japan, Italy, Belgium, the USA and Denmark.
The polypropylene screw cap of the bottle and plug were produced in Denmark
and transported to Sweden. Additional low-density polyethylene shrink-film
and corrugated cardboard were used to distribute the final product. Other
ingredients such as sugar, vinegar, spices and salt were also imported. The
bottled product was then shipped through the wholesale retail chain to shops,
and bought by households, where it is stored refrigerated from one month to
a year. The disposal of waste package, and the treatment of wastewater for
the production of ketchup and sugar solution (from beet sugar) were also included
in the accounting.
of the whole system was split up into six subsystems: agriculture, processing,
packaging, transport, shopping and household.
There are still
many things left out, so the accounting is nowhere near complete: the production
of capital goods (machinery and building), the production of citric acid,
the wholesale dealer, transport from wholesaler to the retailer, and the retailer.
Likewise, for the plastic bottle, ingredients such as adhesive, ethylenevinylalcohol,
pigment, labels, glue and ink were omitted. For the household, leakage of
refrigerants was left out. In agriculture, the assimilation of carbon dioxide
by the crops was not taken into consideration, neither was leakage of nutrients
and gas emissions such as ammonia and nitrous oxide from the fields. No account
was taken of pesticides.
the energy use and carbon emissions for each of the six subsystems from the
diagrams provided in the research paper, and have taken the energy content
of tomato ketchup from another brand to present their data in another way
(Tables 1 and 2), taking the minimum values of energy and emissions costs.
|Table 1. Energy Accounting for 1 kg Tomato Ketchup|
|Packaging||7.8 (without waste incineration)|
| ||6.0 (with waste incineration)|
|Household||1.4 (refrigeration for one month)|
| ||14.8 (refrigeration for one year)|
|Energy in 1 kg tomato paste||0.00432|
|Energy use per GJ tomato paste||4 190|
|Table 2. Carbon Dioxide Accounting for 1 kg Tomato Ketchup|
|Subsystem||Carbon dioxide equivalent kg|
|Packaging||1 275 (without incineration)|
| ||2 315 (with incineration)|
|Total (minimum)||2 290|
As can be seen, it
takes at least 4190 units of energy to deliver 1 unit of ketchup energy to
our dinner table, with at least 2 290 kg of carbon dioxide emissions per kg
food processing were the hotspots for many impacts. But at least part of the
packaging is due to the necessity for long distance transport. Within the
household, the length of time stored in the refrigerator was critical.
the agricultural system is an obvious hotspot. For nitrous oxide emissions,
transportation is another hotspot. For toxicity, the agriculture, food processing
and packaging were hotspots, due to emissions of sulphur dioxide, nitrogen
oxides and carbon monoxide; also heavy metals, phenol or crude oil. If leakage
of pesticides, their intermediates and breakdown products had been considered,
then agriculture would have been an even worse toxicological hotspot.
As regards the
capital costs for tomato cultivation omitted from the study, literature from
France gave a value of 0.180GJ/kg. As regards the wholesale and retail step
left out of the study, literature data indicate 0.00143GJ/kg beer for storage
at wholesale trader in Switzerland and 0.00166GJ/kg bread in the Netherlands.
There is clearly a lot of scope in reducing transport, processing and packaging,
as well as storage in our food system, all of which argue strongly in favour
of food production for local consumption in addition to adopting organic, sustainable
agricultural practices. An integrated organic food and energy farm that turns
wastes into resources can be the ideal solution to reducing greenhouse gas emissions
at source, decreasing environmental pollution, reducing transport, and increasing
energy efficiencies to the point of not having to use fossil fuels altogether
 (Dream Farm 2, Organic, Sustainable, Fossil Fuel Free, In Food
Futures Now, ISIS Publication).
it is feasible to reduce the energy consumption and carbon emissions by 50
percent, at least partly due to localising food systems, this could save 3.5
percent of global energy use and 1.5 percent of global ghg emissions.
Total mitigating potential of organic sustainable food systems
estimates of the potential of organic sustainable food systems to mitigate
climate change based on work reviewed in this Chapter are presented in Box
| Box 2 Global potential of organic sustainable food systems for mitigating climate
|Greenhouse gas emissions|
|Carbon sequestration in organic soil||11.0 %|
|Localising food systems|
| Reduced transport||10.0%|
| Reduced processing & packaging||1.5 %|
|Phasing out N fertilizers|
| Reduced nitrous oxide emissions||5.0 %|
| No fossil fuels used in manufacture||2.0 %|
|Localising food system|
| Reduced transport||10.0 %|
| Reduced processing & packaging||3.5 %|
|Phasing out N fertilizers|
| No fossil fuels used||3.0 %|
The total mitigating potential of organic sustainable
food systems is 29.5 percent of global ghg emissions and 16.5 percent
of energy use, the largest components coming from carbon sequestration and
reduced transport from relocalising food systems.