Biochar: "A castle in the air or a real option for climate change mitigation?" David Manning

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2 Biochar: "A castle in the air or a real option for climate change mitigation?" David Manning Professor of Soil Science Director, Institute for Research on Environment and Sustainability Newcastle University, UK and UK Biochar Research Centre david.manning@ncl.ac.uk UKBRC

3 What is Biochar? Biochar is the carbon residue produced after partial combustion of biomass from any source. Charcoal is one example of biochar. In the context of climate change mitigation, biochar is produced by biomass pyrolysis as part of a bioenergy project.

4 Why is Biochar interesting? Depending on how it is produced and then used, biochar offers the possibility of combining energy generation and carbon capture. Biochar is one of very few processes that remove C from the atmosphere. Is this to good to be true? This presentation looks at some of the evidence.

5 The soil carbon cycle Exchange of carbon between plants, the soil and the atmosphere exceeds the amount exchanged between the ocean and the atmosphere. As land-living creatures with a long history of agriculture, we can exploit this. About a sixth of ALL of the carbon in the atmosphere passes through the plant-soil system annually. Biochar captures some of this carbon.

6 The soil carbon cycle Photosynthesis removes: 160 GT/yr Plant respiration returns: 80 GT/yr Soil respiration returns: 80 GT/yr Remember, the atmosphere contains 720 GT of C The ocean exchanges about 107 GT/yr

7 The soil carbon cycle Photosynthesis removes: 160 GT/yr Plant respiration returns: 80 GT/yr Soil respiration returns: 80 GT/yr How can we capture photosynthesised carbon and keep it in the soil?

8 Soil carbon sinks: Groundwater Soil carbonate minerals Soil organic matter

9 Soil carbon sinks Photosynthesis removes: 160 GT/yr Plant respiration returns: 80 GT/yr Soil respiration* returns: 80 GT/yr *includes compost Soil sinks? GT/yr

10 How does Biochar fit in to this? Adding biochar to soil acts as a carbon sink, because char is stable in soils for hundreds, perhaps thousands of years (we know this from archaeological records), or millions of years (from the geological record). Key questions arise: 1)How do we make biochar? 2)Where will all the biomass come from that we need to make biochar? 3)How does biochar work in carbon capture? 4)Can biochar make a difference? 5)Is biochar safe? 6)If biochar is so good, why aren t we using it already?

11 How do we make Biochar? Typically, biochar is produced using a pyrolysis system that is coupled to a generator, to produce electricity: Biomass Pyrolysis unit No oxygen C Oils & gases Generator system Green electricity Biochar

12 Where could all the biomass come from? In the EU, we generate about 3 billion tonnes of waste annually. About 130 million tonnes is used for energy recovery or incinerated. Agricultural waste is about 700 million tonnes. Sewage sludge is about 9 million tonnes. There is no shortage of biomass in Europe! 5 tonnes of dry biomass can give 1-2 tonnes of biochar EU agricultural waste could give >100 million tonnes of biochar Source:

13 How does Biochar work in carbon capture? Sequestration of carbon as a stable biochar soil pool Displacement of carbon-positive fossil fuel energy Increase in soil fertility (reduced fertiliser use; increased net primary productivity) Reduction of nitrous oxide emissions Read: Gaunt and Lehmann, Environ.Sci.Technol. 2008, 42,

14 Biochar carbon capture benefits: Annual carbon savings tonnes / ha Combustion Pyrolysis Fossil fuel offset Biochar in soil Other stabilisation in soil -? Reduced fertiliser Reduced N2O emission Total From Saran Sohi, UK Biochar Research Centre

15 Can Biochar make a difference? Most experts consider that it is feasible to have a target of 1 GT C removal from the atmosphere using biochar. This is an eighth of what is required, and is similar to contributions expected to be made individually by other renewable energy systems. This figure is based on use of agricultural wastes and similar materials as a source of biomass, and no competition with food production.

16 Can Biochar make a difference? Scenarios calculated by the International Biochar Initiative suggest that a 1 GT C/yr target can be reached by Figures from:

17 Is Biochar safe? As a material, biochar is intrinsically no more hazardous than charcoal, which we are happy to use for a range of different purposes. But if we use a waste stream as our source of biomass, of course we need to carry out an assessment of possible risk. The tools that we need to do this are readily available (e.g. used for compost, sewage sludge), and environment agencies have appropriate experience and expertise.

18 Why don t we use Biochar already? Many reasons. 1)In Europe, momentum is slowly building. a) Available technologies seem unfamiliar b) Investment costs are significant c) Little incentive to add biochar to soil (very few trials under European conditions) d) Other energy generating systems appear to be more attractive We need demonstration sites and strategic research for European conditions 2)In countries with deeply weathered soils that do not retain nutrients well, the very high cost of fertilisers (especially K) makes biochar attractive

19 A castle in the air? No. If we want to stabilise atmospheric CO 2 at 450 ppm (Vattenfall, 2007), we have to REMOVE the equivalent of 27 GT CO 2 by 2030 (7-8 GT C). Most strategies at present are designed to reduced the rate of increase of CO 2 emissions, by substituting for fossil fuel use. Biochar provides a potentially significant way to contribute to the Vattenfall target, as it is one of very few large scale (in aggregate) technologies that take C out of the atmosphere. Source:

20 A real option? Yes, provided we have the will to make biochar happen. Biochar use must be sustainable. Biochar can be integrated with: 1)Electricity generation (especially rural) 2)Waste management 3)Land restoration 4)Land management and planning 5)Biofuel feedstock production

21 THANK YOU