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Biochar and organic waste in soils: global warming mitigation and SOM quality
Convener: Gabriel Gascó Guerrero  | Co-Conveners: Ana Maria Tarquis , Heike Knicker , Agustin Merino , Ana María Méndez Lázaro , Jorge Paz-Ferreiro 
 / Tue, 29 Apr, 13:30–17:15
 / Attendance Tue, 29 Apr, 17:30–19:00

Biochar has attracted a great deal of attention in the last years and it has been proposed as a geoengineering approach to promote soil carbon sequestration and thus help to mitigate global warming. Biochar addition to tropical soils resulted in the build up of soil carbon pools and has created a type of anthropic soils (Terras Pretas) which higher carbon stocks and fertility levels than the surrounding ferralsols. However, there are still many uncertainties that prevent biochar widespread use in soils, as biochars prepared from different sources and in different conditions will behave in a different manner when added to soils with contrasting properties.
On the other hand, intensive soil management and the excessive use of chemical fertilizers have led to degradation of soil, pollution of waters and emission of GHG to the atmosphere. The depletion of SOM affects soil fertility, sustainable food production and other benefits derived from soil. Strategies for recycling urban and industrial organic waste in agriculture must be developed in response to the increased production of such residues. Wastes can be applied directly to soil or after valorisation processes such as composting and thermal treatment (to produce biochar or ashes). There are many examples of how organic amendments are used to replenish SOM. Changes in SOM content and quality are determined by the composition of the biochar or waste. Understanding the changes that take place in SOM dynamics after application of the amendments is important for preservation of the multiple functions of soils.
There are important gaps of knowledge as regards how the application of organic amendments affects the quality of SOM. This is partly due to the lack of analytical procedures that could be used systematically to control OM quality in wastes and soils. In recent years, alternative techniques, such as thermal analysis, infrared spectroscopy and others, have been used to study the content of labile and recalcitrant organic matter and the degree of humification of SOM after the addition of different organic amendments.
The two main objectives of this session are:

1.To bring together scientists that are trying to develop a better understanding on the benefits and limitations of using biochar as soil amendments. In this session we welcome studies both in Terra Pretas and in other types of temperate or tropical soils as well as studies including different scenarios in climate change. Emphasis will be put in the effects of biochar on pollutant fate, carbon sequestration, soil nutrient transformation and leaching and soil microorganisms. Also, studies about the effect of different pyrolysis conditions on biochar are welcomed.

2.To identify indicators for evaluating the quality of organic wastes and for assessing the efficiency of organic amendments from the point of view of SOM quality and C sequestration

Funding provided by CEIGRAM (Research Centre for the Management of Agricultural and Environmental Risks)is greatly appreciated.