Every year the level of carbon dioxide in the atmosphere goes up by 2 parts per million (ppm) and has gone from 280 ppm in 1850 to 402 ppm today. When carbon is burned it produces 3.67 times as much carbon dioxide (CO2) by weight. Oil by weight is at least 80% carbon, so burning a tonne of oil releases just over 3 tonnes of carbon dioxide. Biochar is 75% carbon. Incorporating one tonne of biochar into the soil is the equivalent of keeping 3 tonnes of CO2 out of the atmosphere. So 1 tonne of biochar offsets the emissions from 1 tonne of oil.
Current estimates put the total net annual increase at 4.3 billion tonnes of Carbon. This is why CO2 concentrations in the atmosphere have risen from 280ppm to 402ppm and is closely associated with recent, visible changes to the global climate, particularly temperature rise. To have a 50% chance of keeping this rise to less than 2°C the scientific view is that we should limit further CO2 emissions to 500 ppm.
The implication of the Paris Agreement is that, quite quickly, we will need to balance anthropogenic sources and sinks of carbon dioxide – certainly well before 2050. Ultimately we must begin to reduce the level of atmospheric CO2.
The ‘4 per 1000 Initiative’ announced in Paris aims to put 4 kilos of organic matter per tonne of soil, as this would be enough to completely offset the annual increase in greenhouse gas. The world’s soils comprise 9 billion hectares and contain 1500 billion tonnes of carbon. So adding 6 billion tonnes of carbon every year to soil would stabilize the annual increase in CO2. That’s just over half a tonne of carbon per hectare. This can be done by increasing soil organic matter with cover crops, manure, compost, agroforestry and mulches. Adding biochar adds to this mix of activities and enhances the rate of growth of soil organic matter, while reducing erosion and rebuilding fertility in degraded soils.
Markets are starting to trade in soil sequestration credits with methodologies already agreed in areas of the US and Canada at values of 2.7t CO2/per ton of biochar. The economic drivers have proven that biochar as a soil amendment can deliver meaningful economic return in terms of increased horticultural productivity and vitality in the long term. Rewarding farmers and growers who apply biochar for its carbon sequestration value will add to the multiplicity of benefits to soil health and biodiversity that biochar delivers.
Biochar is one of the best options we have – it is available and scalable, and now viable. However we cannot realise its full potential while carbon pollution remains unpriced and initiatives for soil sequestration lack focus. The voluntary market for carbon supports biochar-based credits and California has now begun accepting biochar carbon credits as part of their statutory system.