Your article "Ancient skills could reverse global warning" (7 December) claims that a multimillion-dollar investment into biochar (charcoal left over from bioenergy production which is used as a fertiliser) will mitigate climate change by taking carbon dioxide from the atmosphere and storing it in soil. There is no evidence to prove that biochar will do any of this. The chair of the International Biochar Initiative board, Johannes Lehmann, stated in a peer-reviewed article that there are still major uncertainties, including how long the carbon will actually remain in the soil, or how to add it without increasing soil erosion and soil carbon losses. Nobody knows for certain how terra preta soil in Brazil was created and nobody has been able to replicate the practices used to create it.
A large-scale biochar industry, perhaps sustained by carbon trading and high fertiliser prices, can be expected to put new pressures on forests and other ecosystems, as large quantities of wood and other biomass will be required, on top of already unsustainable demands for pulp and paper, biofuels and other products.
The climate and humanitarian disaster caused by land conversion, including deforestation for biofuels, could soon be replicated by a new global biochar industry.
Almuth Ernsting and
Great. Steal the knowledge, patent it, and sell it back to the Indians... the genesis of all climate change.
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Like millions of Britons, I am sure, I have not the slightest interest in the puerile antics of celebrities ("What is Britain's obsession with celebrities about?", 7 December). Mark Booth says that his teenage children couldn't understand what the fuss was about, with regard to the Brand/Ross affair. This is just an example of how uncouth behaviour and lack of respect are creating a world where anything goes, and where it is considered OK to be cruel and crude, no matter what the consequences. There is not a generation divide here, but a divide between those of us who understand the results of such actions and those who do not.
Booth ends by posing the question "If celebrity is a state of incipient psychosis, what is sharing the same mental space as celebrities doing to the rest of us?". The answer is not to become involved in the psychosis in the first place.
Your article on gender-bending chemicals raises a valid concern but the attempt to link it to proposed EU legislation on pesticides was unjust ("Men really are the weaker sex", 7 December). Pesticides are the most highly regulated group of chemicals in Europe and UK farmers have adopted voluntary measures such as annual sprayer testing which go beyond legal requirements. However, we believe the regulatory system should be based on sound science and that the same rules should apply to EU imports as well as to food produced in the EU.
Stoneleigh Park, Warwickshire
The British Plastics Federation urges caution when reporting links between flame retardants and phthalates used in plastic products and the "feminisation" of animals. These are some of the most widely studied chemicals and their use has consistently been found to be safe. Chemical safety is of paramount importance to the plastics industry, which invests heavily in researching the substances it uses. Moreover, the European Chemical Regulation, Reach, will ensure further rigorous evaluation and testing.
British Plastics Federation
Of course so-called lads' magazine should be kept out of the reach of children ("Lads mags to be for 'adults only'", 7 December). Even more harmful are the motoring titles that glamorise fast cars and, by implication, encourage driving at dangerous and illegal speeds. They should be open to prosecution for incitement to law-breaking, as should the BBC, for Top Gear.
In Australia, the date for starting school is 1 July, the midpoint of their academic year ("Children may start school at four", 7 December). This means children have students six months older or younger than themselves, at most. Instantly the "summer-born" effect is halved.
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Our children go to school far too early and have to cram learning, tests and exams in from a young age. They can benefit just as much by spending time with a parent or carer doing fun and interesting things, often on a one-to-one basis.
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Kevin Rawlings asks for a menu for a good Christmas dinner for two (Letters, 7 December). May I suggest chestnut and cranberry en croûte, or a recipe from our website, www.animalaid.org.uk? They are delicious and cruelty-free, which is appropriate at this time of peace and goodwill. Happy Christmas.