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

David ManningProfessor of Soil ScienceDirector, Institute for Research on Environment and SustainabilityNewcastle University, UKand UK Biochar Research Centre

david.manning@ncl.ac.ukUKBRC

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.

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.

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.

The soil carbon cycle

Photosynthesisremoves:160 GT/yr

Plant respiration returns:80 GT/yr

Soil respirationreturns:80 GT/yr

Remember, the atmosphere contains 720 GT of CThe ocean exchanges about 107 GT/yr

The soil carbon cycle

Photosynthesisremoves:160 GT/yr

Plant respiration returns:80 GT/yr

Soil respirationreturns:80 GT/yr

How can we capture photosynthesised carbon and keep it in the soil?

Soil carbon sinks:

Groundwater

Soil organic matter

Soil carbonate minerals

Soil carbon sinks

Photosynthesisremoves:160 GT/yr

Plant respiration returns:80 GT/yr

Soil respiration*returns:80 GT/yr

Soil sinks? GT/yr

*includes compost

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?

How do we make Biochar?

Typically, biochar is produced using a pyrolysis system that is coupled to a generator, to produce electricity:

Pyrolysis unitNo oxygen400-600°C

Oils &gases

Green electricity

Biochar

Biomass

Generator system

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 biocharEU agricultural waste could give >100 million tonnes of biochar

Source: http://ec.europa.eu

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, 4152–4158www.biochar-international.org

Biochar carbon capture benefits:

Fossil fuel offset 0.9 0.7Biochar in soil - 0.5Other stabilisation in soil - ? Reduced fertiliser - 0.1Reduced N2O emission - 0.5

Total 0.9 1.8

PyrolysisAnnual carbon savingstonnes / ha

Combustion

From Saran Sohi, UK Biochar Research Centre

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.

Can Biochar make a difference?

Scenarios calculated by the International Biochar Initiative suggest that a 1 GT C/yr target can be reached by 2020.

Figures from: www.biochar-international.org

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.

Why don’t we use Biochar already?

Many reasons….1)In Europe, momentum is slowly building.

a) Available technologies seem unfamiliarb) Investment costs are significantc) Little incentive to add biochar to soil (very few trials

under European conditions)d) Other energy generating systems appear to be more

attractiveWe 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

A castle in the air?

No.

If we want to stabilise atmospheric CO2at 450 ppm (Vattenfall, 2007), we have to REMOVE the equivalent of 27 GT CO2 by 2030 (7-8 GT C).

Most strategies at present are designed to reduced the rate of increase of CO2 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.

www.vattenfall.com

Source: www.esrl.noaa.gov

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 management3)Land restoration4)Land management and planning5)Biofuel feedstock production

THANK YOU