The current (late 2010) concentration of CO2 in the atmosphere is 390 ppm. Because of the delay between rising levels of CO2 and its full impact on climate, many people are complacent about it. However, scientists advise that such a level is already above the concentration of 350 PPM that they consider safe in the long term. Therefore an effective global solution must not just be concerned with restricting new emissions of CO2, but also with the long and difficult process of removing the pollution already in the atmosphere. With that insight, this web site examines the costs of sequestering CO2 at the same time as it examines the costs of renewable energy. This then allows the carbon price required to achieve emission reduction targets to be calculated. The various technologies for sequestering CO2 are listed below in order of estimated cost. The cost unit is US dollars per tonne (1000kg) of CO2.
It is perhaps not surprising that the cheapest form of CO2 sequestration is the way nature does it - trees! An excellent paper that demonstrates this is "The Cost-Effectiveness of Carbon Sequestration in Harvested and Unharvested Eucalyptus Plantations" by A. J. Richardson. He notes that here are three major advantages of harvesting a plantation primarily designed for carbon sequestration. Firstly, by harvesting trees which have reached maturity (and effectively stopped absorbing carbon dioxide) and replacing them with a new planting of rapidly growing new trees, the total sequestration can be increased over the long-term compared to leaving the original plantation in place. Secondly, as well as sequestering carbon in growing trees, harvesting allows carbon to be sequestered for long periods in a succession of timber products. Thirdly, the income obtained from harvesting cross-subsidises the costs involved in planting for sequestration, thereby improving the cost-effectiveness of the carbon sequestration. While the article looks at Eucalyptus, in other parts of the world other species such as Radiata Pine might be used. One of the assumptions in the Kyoto Protocol about carbon sequestration in plantations is that if the plantation is harvested at some point in the future, then all the carbon that has been sequestered during the life of the plantation is immediately released back into the atmosphere. Richardson notes that timber used in building has a life of up to 90 years, but a method of accounting needs to be devised if this form of sequestration is to have a place in the market. While I believe it is the cheapest means of carbon sequestration, it requires land which is a limited resource. It is suited to terrain presently used for forestry or grazing, but should not use arable land at the expense of food crops.
Unharvested plantation timber is still a relatively cheap form of sequestration, but the problem is it requires much more land than harvested timber. In fact, because mankind has been using coal, formed from the remains of plants over millions of years, there is not enough land on Earth for unharvested timber to soak up the excess CO2 already in the atmosphere. This method of sequestration is most suited to rugged land in which harvesting is difficult.
At the Australian Government Healthy Soils Symposium, Dr Michael Robinson, Land and Water Australia executive director and former CEO of the Cooperative Research Centre for Greenhouse Accounting expressed the view that soil carbon sequestration was unlikely to play a large role in carbon trading schemes in the short term. "Verification costs make soil carbon trading untenable with carbon prices as they are. Most schemes define permanence as 70 to 100 years. A contract will stipulate that carbon must be sequestered for that time period. So, in a mandatory scheme, landholders will need to verify that carbon has been sequestered permanently. Carbon is traded in NSW for about $A15 a tonne of carbon dioxide equivalent. In the EU market it has been about $A40 a tonne."
Charcoal is nearly pure carbon, so a tonne of charcoal is equivalent to 3.5 tonnes of CO2. Agricultural charcoal currently sells in the US for $500 per tonne, equivalent to 500 / 3.5 = $143 per tonne of sequestered CO2. Biochar can be sold as agricultural charcoal, but if produced on an industrial scale its price would be significantly lower, and after the cost of feedstock and transport might only make a net $100 per tonne, equivalent to 100 / 3.5 = $28 per tonne of sequestered CO2. However, the production of biochar through the pyrolysis of biomass also creates a combustible gas as a byproduct which is a source of clean energy. Factoring in a net profit of this gas of $50 per tonne of sequestered CO2, my estimate for the cost of carbon sequestration using biochar is 143 - (28 + 50) = $65 per tonne.
This section is under construction.
This section is under construction.