Climate farming
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Climate farming is the name given to a carbon farming concept that focuses heavily on the use of biochar and aims to reduce climate-damaging gases in the earth's atmosphere through the use of modern agricultural methods. In climate farming, secondary crops and ecological compensation areas are created in order to use the biomass produced on these areas to produce energy and biochar and to increase the humus content in the soil. The associated carbon sequestration in the soil is being scientifically investigated in various research projects.
State of research[edit]
The relevant climate-damaging gases in agriculture are carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O). Methane is mainly produced when growing rice and raising livestock , but also when biomass rots , for example in manure . Nitrous oxide (also called nitrous oxide ) is released by nitrogen fertilizers . A lot of carbon dioxide is produced by deforestation and slash-and -burn agriculture .
How much carbon dioxide remains in the soil during cultivation, for example in arable farming , depends on the balance of carbon inputs into the soil (e.g. through crop residues such as stubble or roots , or farmyard manure such as manure) and the carbon losses from the soil (usually through respiration , aggravated by soil disturbances). There is a constant breakdown and buildup of humus in the soil. In a stable ecosystem (e.g. forest , old grassland ) both processes are balanced, i.e. H. the humus content hardly changes. At the Chair of Forestry Economics, Faculty of Economics, Technical University of Munich , carbon sequestration in forest management in Cameroon was examined as part of a dissertation in 2016 . Further studies on carbon storage have been carried out for many years at the Chair of Soil Science, Weihenstephan Science Center for Nutrition, Land Use and Environment, Technical University of Munich.
When growing energy crops , the aim is to obtain as much biomass as possible, which can then be used for energy purposes. Reducing carbon dioxide emissions to reduce the greenhouse effect is an important factor. The climate impact of the cultivation and use of energy crops is controversially discussed. In addition to the CO 2 savings through the use of renewable raw materials, the climate balance of arable farming must also take into account the climate-relevant emissions of nitrous oxide N 2 O, which is mainly produced by nitrogen-fertilized arable crops.
→ Main article : Carbon sequestration in the soil #Deep plowing
There are studies from Germany and New Zealand on deep plowing that show that shifting carbon that is not easily degradable to greater depths in the soil, where it is stored due to longer residence times, can make a contribution . Application on 5000 hectares of soil offers an annual potential of 15.4 million t CO 2 over 20 years as part of CO 2 sequestration ; this corresponds to an annual potential of 770 kt CO 2 per year.
However, in some soils there is a risk that an existing humus layer will be destroyed, which has a negative impact on soil fertility .
Use of biochar[edit]
Biochar can be obtained through pyrolysis of organic base materials such as wood , straw , wine pomace , green waste , but also manure, sewage sludge or kitchen waste . First, the biomass is dried, which is then heated to temperatures of 400 to 800 degrees in the absence of oxygen, whereby the long-chain carbon compounds of the organic cells are broken. This produces synthesis gases and up to 40% biochar, the consistency of which corresponds to that of normal barbecue charcoal. Using controlled smoldering chambers and the flox process, the energy-rich synthesis gases can be burned with low levels of pollutants. The resulting waste heat can be used for heating purposes or converted into electricity via combined heat and power .
In the 1.5°C Global Warming special report published in October 2018 , biochar was first mentioned by the IPCC as a promising negative emissions technology (NET). However, studies on the climate impact of the production and use of biochar are in the background compared to other NETs. At the last world climate conference in Katowice, December 2018, there was no decision to integrate such sequestrations into global carbon trading .
Climate footprint of biochar[edit]
→ Main article : Biochar #carbon sink
Biological residues such as green waste, pomace or manure are usually used either through composting or through rotting. If you work the biochar into the soil, you permanently remove carbon from the atmosphere, which can no longer contribute to global warming . Since the energy from the synthesis gas can also be used to generate electricity and thus replace fossil fuels, the climate impact of the pyrolysis of biological residues is almost 95% climate positive compared to simply rotting them.
In view of the scarcity of biomass that can be meaningfully used for charring there is a risk that widespread use - and possibly promotion - of pyrolysis will result in the use of valuable wood stocks or even contaminated smolderable waste.
Soil improvement through biochar input[edit]
→ Main article : Biochar #Biochar as a soil improver
The soil input of biochar is not only interesting from a climate policy perspective, but also from an agronomic point of view. In relevant scientific studies the following advantages for soil cultivation have been proven:
- Improving water storage capacity, enabling savings in artificial irrigation and replanting of dry areas
- Increase in root mycohorrices for improved mineral absorption
- Greater soil aeration and thus reduction of methane and nitrous oxide emissions
- Improvement of the cation exchange capacity for the substance balance of plants
Depending on the crop grown, between 10 and 120 t of biochar are added to the soil per hectare, binding the equivalent of 36 to 440 t of CO 2 per hectare. If some of the biochar produced from biomass were used to generate electricity and the agricultural machines were largely converted to electricity and battery operation, agriculture would no longer be responsible for 14% of climate-damaging emissions [12], as is currently the case, but would operate in a climate- manner .
The German Federal Environment Agency (UBA) and the Federal Institute for Geosciences and Raw Materials (BGR) warn of potential risks regarding the effects on soils and crops given the large number of raw materials, manufacturing processes and areas of application. In 2016, the German UBA recommended further systematic investigations and the establishment of a certification system.
Non-agricultural fields of application[edit]
Pyrolysis can also be used very efficiently in the recycling of waste materials. This means that sewage sludge can be pyrolyzed into biochar and energy, as well as residues from biogas plants , pressed residues from sunflower oil, rapeseed oil or olive oil production, and fermentation residues from bioethanol production . Pyrolysis can also be used to supplement waste incineration plants. Even if the biochar from sewage sludge or waste disposal cannot be used to improve agricultural soils, the biochar could still be stored permanently in old mines, where they form carbon sinks .
See also[edit]
Literature[edit]
Individual evidence[edit]
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