The use of large-scale afforestation, bio-char production and biomass carbon capture and storage have some limited carbon reduction potential but there are very significant land use issues associated with these. These geoengineering techniques could seriously compete with land needed to produce food (the quantity of land required varies hugely dependent on diet) and land for the protection of ecosystems. Until these land-use issues are better understood Friends of the Earth cannot support the use of large-scale afforestation, bio-char production and biomass carbon capture and storage.
Chemical air capture of carbon is the most promising carbon reduction option, although some research is still needed into safe storage sites. This is a very expensive option which is far more costly than mitigation. However rich countries have already far exceeded their fair share of “environmental space” through releasing far more than their fair share of carbon emissions over the last 200 years. If safe storage sites can be identified rich countries should carry out significant air capture of carbon, in additional to very significant cuts in emissions.
The problem with this analysis is the apples and oranges comparisons of costs. Chemical capture can only be done at great cost per unit of carbon reduction, so FOE assumes that large costs are allowable for chemical capture but not for the biological techniques. OTOH, if you assume you're allowed to spend the same amount on biomass or biochar, you can solve at least some of the problems that FOE identified with them. At least you could provide incentives to use non-agricultural land for biomass production. This might still produce pressure on natural habitat, but if we're assuming lots of money, there's ways to deal with that too, like paying for increased productivity on farmland instead.
Of course I'm just waving my hands at cost figures instead of crunching them, but that still puts me one step ahead of FOE. Somebody needs to do the numbers. Roger claimed to have done the numbers, but 1. his work generally raises doubts in my mind and I'm not going to spend time checking every citation to determine whether it says what he claims it says; 2. he only examines capture costs, not sequestration costs, transport, monitoring, technology development etc ("In this paper I explore some of the economic considerations associated with air capture of carbon dioxide, and do not address issues of storage, which are explored in depth elsewhere"); and 3. he does his own apples to oranges thing of comparing the partial costs of capture to full costs of mitigation in the Stern Report and IPCC (in part 4.1: "If air capture technology could be implemented at [lowest rate cited by Roger], then the cost to stabilize emissions over the 21st century would be less than the Stern median estimate....The IPCC median value of 1.3% [of global GDP] is less than the costs air capture [sic] at $360 cost per ton of carbon, but almost three times the cost at $100 per ton.")
I hope FOE reconsiders its analysis sometime on an apples to apples basis. I wouldn't rule out chemical capture, but it needs to considered realistically.