ministry of food agriculture and fisheries danish institute of agricultural sciences options for...

Ministry of Food Agriculture and FisheriesDanish Institute of Agricultural Sciences

Options for reducing the greenhouse gas emissions from agriculture

Jørgen E. Olesen


Greenhouse gases and international commitments

Carbon dioxide (CO2), methane (CH4), nitrous oxide(N2O) and CFC gases are the most important greenhouse gases causing global warming.

The Climate Convention from 1992 commits industrialised countries to stabilise their emissions of greenhouse gases.

The Kyoto Protocol from 1997 is an international agreement on reduction of greenhouse gas emissions through a number of mechanisms. EU must reduce the emissions by 8% and Denmark by 21% before 2008/12.


Greenhouse gas emissions from Denmark

Emissions in mill. ton CO2-equivalents per year

The greenhouse gases have different global warming potentials: The global warming potential of methane (CH4) is 21 times greater than CO2

The global warming potential of nitrous oxide (N2O) is 310 times greater than CO2

1990 2003 2008-12 Carbon dioxide (CO2) 52.9 59.2 59.0 Methane (CH4) 5.7 5.9 5.6 Nitrous oxide (N2O) 10.7 8.1 6.9 Industrial gases 0.3 0.7 0.8 Total 69.6 73.9 72.3 Electricity export -6.3 6.9 4.4 Kyoto target (-21%) 55/ 60 Reductions in other countries 4.5 Deficit 7,8/ 12,8


Fulfilling the Kyoto targets

• It is the objective of the Danish government that the commitments are distributed between sectors in a balanced way.

• Initiatives for reducing emissions are evaluated on their cost-effectivness against a benchmark of 120 DKK per ton CO2.

• The emissions from the energy sector and some other industries are regulated by tradable quotas.

• Sectors without quotas (including agriculture) will also need to reduce emissions. Otherwise there will be a need to tighten the quotas for the energy sector.


Greenhouse gas emissions from Danish agriculture


Development in agricultural emissions of N2O og CH4

• The Aquatic Action Plans have led to a total reduction in nitrous oxide emissions of about 2.2 mill. ton CO2-eq per year

8

9

10

11

12

13

14

15

16E

mis

sion

s (m

ill. t

CO

2-eq

. yr-1

)

Without measuresWith measures

Effect of Aquatic Action Plans


Model estimated carbon content in Danish mineral soils

The changes around 1990 are caused by a ban on field burning of straw

1980 1990 2000 2010 2020

Car

bon

in m

iner

al s

oils

(m

ill.

ton

C)

426

428

430

432


Reduction of greenhouse gas emissions

Gas Principle Method (examples)

CO2 Energy savings Climate control Reducered tillage

Energy production Straw + energy crop Biodiesel + bioethanol Biogas

Carbon storage Forestation Reestablishment of wetlands Permanent grasslands Reduced tillage


Reduction of greenhouse gas emissions

Gas Principle Method (examples)

CH4 Reduced activity Fewer animals

Lower emission factor

Changed feeding Methane inhibitors Methane oxidation

Collection of CH4 Anaerobic digestion (biogas)

N2O Reduced activity Improved fertiliser N

Lower emission factor

Anaerobic digestion (biogas) Burn the solid manure fractions Nitrification inhibitors Better timing of applications Biological N fixation


Cost-effective reduction measures

Reduction potential mill. ton CO2/ year

Costs DKK/ ton CO2

Increased fat in feed for cows 0.45 -55 Changed feed for dairy cattle 0.10 <120 Airtight sealing of solids manure heaps

0.05 <120

Biogas (additional 10% of slurry) 0.23 43 Nitrification inhibitors in fertiliser 0.30 0 til 1500 Energy crops - willow 0.40 -40 til 50 - cereals 0.26 50 - straw 1/ 3 is used today <120 Forestation 0.03 -500 til 900


Biogas

• Energy production (electricity and heat - substitution of fossil energy sources – depends on addition of other organic energy sources)

• Reduced methane emissions (requires collection of methane after the biogas reactor)

• Reduced nitrous oxide from the manure after field application

• The emissions can be reduced by 1.3 to 2.3 mill. ton CO2-eq/yr if all animal manure and organic wastes are used (depending on technology)

1990 1992 1994 1996 1998 2000 2002 2004

En

erg

y p

rodu

ctio

n (

TJ)

0

500

1000

1500

2000

2500


Cover on manure storages

• The methane oxidation in the slurry surface crust is increased at increasing methane concentration (a cover will increase the methane concentration and therefore the oxidation)

• Covers on slurry stores are estimated to reduce emissions by 10-50%. However, an optimised air exchange may further improve methane oxidation

• An airtight cover on solid manure heaps can virtually eliminate emissions of methane and nitrous oxide


Frequent manure removal from the animal house

• Daily removal of slurry from the house to an outside store will reduce the storage temperature (in particular during winter) and thus the methane emissions.

• Daily removal from dairy housing will reduce emissions by up to 50%.

0

0.5

1

1.5

2

2.5

3

0 7 14 21

Temperature, C

Met

han

e p

rod

uct

ion

, g/m

3/h

Pig slurry, 94

Cattle slurry, 94

Cattle slurry, 97a

Cattle slurry, 96

Cattle slurry, 97b


Conclusions

• Methane and nitrous oxide are the most important greenhouse gas emissions from agriculture

• The emissions of methane can be reduced by improving cattle feeding and manure handling

• The emissions of nitrous oxide can be reduced by reducing N losses and improving manure and fertiliser management

• The cost-effective reduction measures reduce the emissions of several greenhouse gases simultaneously.

• Few measures have costs of less than 120 DKK per ton CO2

• The reduction of greenhouse gas emissions should be part of good agricultural practice (green accounting).

ministry of food agriculture and fisheries danish institute of agricultural sciences options for...

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