harvesting%20energy%20with%20fertilizers%20(2002)%20-%20en%20fran%c3%a7ais

8/7/2019 Harvesting%20Energy%20with%20Fertilizers%20(2002)%20-%20en%20fran%C3%A7ais

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Agriculture produces energy

and captures atmospheric CO 2 .Fertilizers greatly increase this effect.

Harvesting Energywith Fertilizers

European Fertil izer M anufacturers Association



x Looking for advanced t echnological solutions thatoptimize the use of existing energy sources.

x Making the use of renewable energy

sources a high priority.

x Finding energy sources which do not acceleratethe greenhouse gas problem, and can even contributeto fixing or binding some CO 2.

Agriculture converts solar energy into biomass, which in turnprovides energy for human beings and animals:

Energy is a central issue in agriculture.The very reason for agriculture’s existence is to supply energy to mankind.It does this by making use of solar power to convert energy into biomass,which in turn supplies energy to human beings and animals in the formof food and feed :

Agriculture produces energy

As the Earth’s non-renewable energy reservesdecline, individuals, public bodies and industries arecoming under pressure to reduce their consumption

of fossil fuels by :



Energy consumption for different economic sectors in West Europe :

x 85% of total energy is consumed by industry,traffic, private households and public services.

x Food production accounts for 15% of this total energy consumption.

x Only 5% is used in agriculture, and this includesthe energy used to produce mineral fertilizers.

Energy consumption in European agriculture:

Of all the energy used to produce wheat, approximately50% is needed to produce, transport and apply nitrogen fertilizers.

Energy consumption in the nitrogen fertilizer chain :

In this chain, most of the energy is required to produce mineral fertilizers, and it is therefore in this area thattechnologies have been developed to ensure that fertilizer manufacturing processes are as efficient as possible.

N, P and K,the three primary nutrients of plants:

N (nitrogen) is an important compo-nent of proteins, and as such is anessential nutrient for plants.

P (phosphorus), component ofnucleic acids and lipids, is also key toenergy transfers in plants.

K (potassium) has an important rolein plant metabolism : photosynthesis,activation of enzymes, osmo-regulation, etc.

* including energy used for the extraction and transport of fossil fuels to the N fertilizer factory (average value for all N fertilizers).

* * transport of N ferti lizer over a distance of 400 km by ship and truck (1 GJ = 25 litres oil)

- values in Giga Joule (GJ) / tonne of N -

Production* :40

Transport* * :1

Spreading :3

P & K fertilizer(production, logistics, application)

8%

Other farm inputs& on field work

40%

N fertilizer(production, logistics, application)

52%

Industry, traffic, householdspublic services85%

Agricultural production(including mineral fertilizer production)

5%

Food industry10%

Source : IFA StatisticsUNEP, World Bank (World Resources 2000-2001)

Source : IFA StatisticsUNEP, World Bank (World Resources 2000-2001)

Energy efficiency is further increasedin the nitrogen fertilizer chain



Technical improvements in mineral nitrogen fertilizer production :

Energy efficiency in N f ertilizer production has been significantlyimproved since the beginning of the 20th century.

Modern fertilizer factories are close to the theoretical minimum of energy consumptionwhen producing ammonia, which is the first step in the production of N fertilizer.

Efficient energy use is also a central issue on farms :

Modern application techniques can help to reduce the amount of energy used byadapting the quantity of fertilizer and the number of applications to the crop’s needs.Grain yield increases as more mineral nitrogen is applied. However, there is aneconomic optimum of N fertilizer rate.

4 5 0

4 0 0

3 5 0

3 0 0

2 5 0

2 0 0

1 5 0

1 0 0

5 0

019 10 1 9 1 5 19 30 1 95 0 19 60 1 97 5 20 00

Theoretical minimum

Birkeland-EydeElectric arc method

Cyanamid-method

Haber-Bosch synthesis Steamreformingnatural gas

Year

G J/ t N

0 4 0 8 0 1 00 1 5 0 2 00 24 0

10

9

8

7

6

5

4

3

2

10

N fertilizer rate, kg/ ha

grain yield, tonnes/ ha

economic optimumN fertilizer rate(170 kg N/ ha)

In these trials the optimum N fertilizer application rate is about 170 kg N/ ha, result ing in a yield of 8.2 tonnes per hectare.At this N rate the farmer's profit per hectare is the highest.This economic optimum is also known to have the best energy used /energy captured rat io.

Source : Anundskas, 2000

Source : Küsters & Lammel, 1999

Evolution of ammonia production efficiency

Economic optimum of nitrogen fertilizer rate



The use of nitrogen fertilizer benefits the environment because it helps to fix extra CO 2 :

x When using solar energy to producebiomass, plants capture atmosphericCO 2 as their main source of carbon.Taking the same example of wheatproduction as above:

- The higher yield obtained withN fertilizer means that more CO 2 is

fixed: 26 tonnes compared with only15 tonnes without N fertilizer.

- The extra 11 tonnes of CO 2captured are more than 5 timesthe volume of CO 2 andother greenhouse gases (N oxides)emitted when producing,transporting and applying fertilizers.

x The CO 2 binding is not permanent,but short to medium term, dependingon the final use of the crop produced (food, feed, industry).

x The CO 2 binding is more permanent when part of the crop is ploughed in, increasing the soil organic content.

Fertilizers greatly increase the positiveenergy balance of agriculture

Energy produced on 1 ha wheat

CO 2 fixed on 1 ha wheat

The use of nitrogen fertilizer enables crops to grow more biomass by helping themto fix additional solar energy:

x When using 170 kg N fertilizer on ahectare of land, wheat yields areapproximately 8.2 tonnes comparedwith 4.7 tonnes without N fertilizer.

x These 8.2 tonnes equate to 126 GJ* ofsolar energy captured in the form ofbiomass when nitrogen is applied,compared with only 71 GJ without Nfertilizer.

x The extra 55 GJ captured whenusing N fertilizers are more than 6 timesthe 8 GJ used to produce, transportand spread the same fertilizers.

28

24

20

16

12

8

4

0

-4

t CO 2/ ha

1515

+11

Biomass(t/ ha, straw + grain)

without N fertilizer with fertilizer170 kg N/ ha

9.4 16.4

-0.7-0.7-2.2

CO 2 captured inextra biomass dueto fertilizer use.

CO 2 captured in basicbiomass productionwithout fertilizer use.

CO 2 emissions* :on field activities etc.N f ertilizer production,transport & spreading.

* including N 2O emissions;1 kg N 2O = 310 kg CO 2.

Grain yield(tonne/ha)

GJ/ t N

1 40

1 20

1 00

80

60

40

20

0

-20

without N fertilizer with fertilizer170 kg N/ha

4.7 8.2

+55

71

-7.5-8

-7.5

71

Solar energy capturedin extra biomass produceddue to fertilizer use.

Solar energy in biomassproduced withoutfert ilizer use.

Energy input due to:on field activities etc.N f ertilizer production,transport & spreading.

Source : Data taken from Küsters and Lammel, 1999.

Source : Data taken from Küsters and Lammel, 1999.

* GJ = Giga Joule

harvesting%20energy%20with%20fertilizers%20(2002)%20-%20en%20fran%c3%a7ais

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