Climate farming

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Climate farming is a concept that 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 accumulating on these areas for the production of energy and biochar as well as for increasing the humus content in the soil. The associated carbon sequestration in the soil is scientifically investigated in various research projects.

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State of research

Cultivation of hybrid poplars as energy wood in a short rotation plantation

The relevant climate-damaging gases in agriculture are carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O). Methane is produced mainly in rice cultivation and the livestock , but also in the decomposition of biomass, for example in the Mist . Nitrous oxide (also called laughing gas ) is released from nitrogen fertilizers . A great deal of carbon dioxide is produced when clearing forests and fire .

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 (mostly through respiration , aggravated by soil disturbances). A constant breakdown and build-up of humus takes place in the soil. In a stable ecosystem (e.g. forest , old grassland ) both processes are balanced, i. H. the humus content hardly changes. At the Chair of Forest Economics, Faculty of Economics, Technical University of Munich , the carbon sequestration in Cameroon in forest management 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 is then to be used for energy. The reduction of carbon dioxide emissions to reduce the greenhouse effect is an important factor. The climate impact of the cultivation and use of energy crops is controversial. In addition to the CO 2 savings through the use of renewable raw materials, the climate footprints of arable farming must also take into account the climate-relevant emissions of laughing gas N 2 O, which is mainly produced by nitrogen-fertilized arable crops.

Deep plowing

There are studies on deep plowing from Germany and New Zealand that show that relocating carbon that is not easily degradable to greater depths of the soil, where it is stored due to longer retention times, can make a contribution. The application on 5000 ha of soil offers an annual potential of 15.4 million tons of CO 2 over 20 years in the context of CO 2 sequestration ; this corresponds to an annual potential of 770 kt CO 2 per year.

In some soils, however, there is a risk that an existing humus layer will be destroyed, which has a negative effect on soil fertility .

Use of biochar

Biochar can be obtained by pyrolysis of organic basic 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, breaking the long-chain carbon compounds of the organic cells. This creates synthesis gases and up to 40% biochar, the consistency of which corresponds to that of normal barbecue charcoal. By means of controlled smoldering chambers and the Flox process , the energy-rich synthesis gases can be burned with low emissions. The resulting waste heat can be used for heating purposes or converted into electricity by means of combined heat and power .

In the special report 1.5 ° C global warming published in October 2018, biochar was first mentioned by the IPCC as a promising negative emission technology (NET). Studies on the climate impact of the production and use of biochar are, however, in the background compared to other NETs. At the last World Climate Conference in Katowice, December 2018, there was no decision to include such sequestrations in a global carbon trade .

Carbon footprint of biochar

Biological residues such as green waste, pomace or manure are usually used either by composting or by rotting. If you work the biochar into the ground, you permanently remove carbon from the atmosphere, which can no longer contribute to global warming . Since the energy of the synthesis gas can also be used to generate electricity and thus replace fossil fuels, the climate balance of the pyrolysis of biological residues is almost 95% climate-positive compared to their mere rotting . Pyrolysis can also be used extremely efficiently in recycling waste. Sewage sludge can be pyrolyzed into biochar and energy, as well as residues from biogas plants , press residues from sunflower oil, rapeseed oil or olive oil production, and fermentation residues from bioethanol production . The use of pyrolysis is also possible in addition to waste incineration plants. Even if the biochar from sewage sludge or from waste disposal cannot be used to improve agricultural soils, the biochar could nonetheless be stored permanently in old mines, where they form carbon sinks .

In view of the shortage of the biomass that can be sensibly used for charring, there is a risk that valuable wood stocks or even contaminated chargeable waste will be used in the widespread application - and possibly promotion - of pyrolysis.

Soil improvement through biochar input

The soil input of biochar is not only interesting from a climatic point of view, but also from an agronomic point of view. In corresponding scientific studies, the following advantages for soil culture could be proven:

  • Improvement of the water storage capacity, which makes savings in artificial irrigation and replanting of arid areas possible
  • Increase in root mycorrhoids for improved mineral absorption
  • Higher soil aeration and thus a reduction in methane and nitrous oxide emissions
  • Improvement of the cation exchange capacity for the metabolism of the plants

Depending on the cultivated crop, between 10 and 120 t of biochar per hectare are introduced into the soil, which binds the equivalent of 36 to 440 t of CO 2 per hectare. If part of the biochar produced from biomass were also 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, but would operate in a climate-positive way.

The German Federal Environment Agency (UBA) and the Federal Institute for Geosciences and Raw Materials (BGR) warn of potential risks with regard to the effects on soils and crops in view of the large number of starting materials, manufacturing processes and areas of application. In 2016, the German UBA recommended further systematic investigations and the establishment of a certification system.

See also

literature

  • Hans-Peter Schmidt: "Terra Preta - Biochar - Climate Farming" in Ithaka - Journal for Terroir Wine, Biodiversity and Climate Farming, St. Gallen 2008, ISSN  1663-0521

Individual evidence

  1. ^ Sabine Fuss, William F Lamb, Max W Callaghan, Jérôme Hilaire, Felix Creutzig: Negative emissions — Part 2: Costs, potentials and side effects . In: Environmental Research Letters . tape 13 , no. 6 , May 21, 2018, p. 063002 , doi : 10.1088 / 1748-9326 / aabf9f .
  2. ↑ http://mediatum.ub.tum.de/1286976
  3. ↑ https://www.boku.wzw.tum.de/index.php?id=dissertations
  4. ↑ Viridiana Alcántara, Axel Don, Reinhard Well, Rolf Nieder: Deep plowing increases agricultural soil organic matter stocks . In: Global Change Biology . tape 22 , no. 8 , 2016, ISSN  1365-2486 , p. 2939-2956 , doi : 10.1111 / gcb.13289 .
  5. Jump up ↑ Marcus Schiedung, Craig S. Tregurtha, Michael H. Beare, Steve M. Thomas, Axel Don: Deep soil flipping increases carbon stocks of New Zealand grasslands . In: Global Change Biology . tape 25 , no. 7 , 2019, ISSN  1365-2486 , p. 2296-2309 , doi : 10.1111 / gcb.14588 .
  6. ↑ Annie Francé-Harrar : The last chance - for a future without need , new edition 2007, page 564
  7. ^ Hans-Peter Schmidt: Biochar and PyCCS included as negative emission technology by the IPCC. In: the Biochar Journal (tBJ), Arbaz, Switzerland. October 19, 2018, accessed June 16, 2019 . ISSN 2297-1114 .  
  8. ↑ Interview with Nikolas Hagemann. Professional Association of Biochar (FVPK), January 23, 2019, accessed on June 16, 2019 .
  9. ^ Teichmann: Climate protection through biochar in German agriculture: potentials and costs. Retrieved February 19, 2020 .
  10. ↑ BUND: Terra Preta / Pyrolysekohle: BUND assessment of their environmental relevance. Retrieved February 19, 2020 .
  11. ^ Bio Char Articles
  12. ↑ WWF - Climate Gases Agriculture
  13. ↑ Biochar: a wide range of properties make generalized statements about the effect on soil functions hardly possible. BGR , accessed on June 16, 2016 .
  14. ↑ a b Opportunities and risks of using biochar and other "modified" biomass as soil additives. (PDF) Federal Environment Agency, 2016, accessed on June 16, 2019 . Brief description.

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