Vapo-rubbish
Your article on vaporising garbage to turn it into fuel shows interesting perspectives on making good use of trash (25 April, p 33). However, the smouldering remains of the World Trade Center should not be compared with high-temperature pyrolysis. The former is low-temperature combustion in ambient air while the latter occurs under controlled conditions.
Two aspects of plasma treatment of material may impede its widespread use. First, the fairly high energy output from the plasma radiates to all surrounding material, including refractory walls, and so is very difficult to direct solely to the trash. One solution is a rotating furnace with a column of arcing plasma at its centre, surrounded by the material to be treated. Such a furnace was developed in France in the 1960s, and has been further refined by the French energy company EDF.
Secondly, plasmas at or near atmospheric pressure have steep temperature gradients at their borders. Material entering this zone experiences temperature conditions that are difficult to control, which may negatively affect the chemistry of the process’s products.
In the past century there has been an extraordinary increase in the volume of trash produced. However, if humans stop making themselves the end-stage of everything and no longer turn all they make or use into waste, products will be designed so that they can be repaired, renovated and reused, with every part salvaged. Progress in design and renovation could reduce resource consumption and emissions more than our current efforts at recycling or vaporising.
Mount Waverley, Victoria, Australia
Baked Earth
If, as Eric Chaisson asserts in “The heat to come…” (4 April, p 24), the second law of thermodynamics makes dangerous global warming an inevitable consequence of further human population growth, then this is primarily driven by our dependence on fossil fuels.
By contrast, plant life has a cooling, entropy-defying impact on the climate. Plants trap solar energy and use it to synthesise complex molecules, where some of it remains stored. Some energy is released again when vegetation breaks down, but decomposition occurs more slowly than growth, so more solar energy is trapped by plant life than is released. Breakdown products are typically more complex than the original constituents used by the plants, so solar energy accumulates in plant matter stored in the soil.
Over billions of years, vast amounts of energy have been sequestered this way, producing peat, coal and oil. These materials are heat sinks for solar energy. To combat global warming, we should take steps to encourage these heat sink systems to trap more energy. This can be done through widespread reforestation and by allowing dead vegetation to decompose naturally.
We need to harness the energy of today’s sun rather than that of yesteryear.
From Steve Cantwell
Chaisson argues that the waste heat output from all energy sources except those derived from solar energy will eventually warm the globe. Unfortunately, though for different reasons, even solar may not be exempt.
If solar energy plants are extensive and replace surfaces that had a higher reflectivity, a significant fraction of the sun’s energy would be converted to Earth-bound heat instead of being reflected back into space.
Chaisson’s article suggests that waste heat will become a problem when demand reaches a “few thousand terawatts”. To generate this, we would need to capture, and convert entirely to heat, several per cent of the solar energy striking the Earth. A future society consuming thousands of terawatts of energy may view desert solar plants to be as globally damaging as we consider fossil fuels today.
Wellington, New Zealand
From Mark Woolrich
Chaisson’s article revisits a scene written by Larry Niven in his 1980 novel Ringworld Engineers, in which he describes how the heat generated by the Puppeteer civilisation on their home world led to them moving it completely out of their solar system to avoid overheating, taking with them four artificially lit “farming” worlds to provide all their food.
How long will it be before New 杏吧原创 reports on this as a solution to our overcrowding and food supply problems?
Wroughton, Wiltshire, UK
In conflict
The editorial and article about “the ghastly experience of being on a battlefield” (25 April, p 3 and p 40) being the cause of mysterious symptoms in war veterans seem to miss a crucial point: unlike the majority of first and second world war veterans, some of the veterans of Vietnam, Iraq and Afghanistan questioned whether they were involved in a just war.
I have talked to members of my family who survived some of the most gruesome battles of both world wars and, although they would never talk about the details, they all believed that they were doing something “right”. They acknowledged that they may have been unduly influenced by the propaganda of their governments, but at the time they were fighting, they believed in their cause.
Many of those who have fought in Vietnam, Iraq and Afghanistan have had to suffer the cognitive dissonance of thinking that either the war itself, or what they were asked to do in its name, was wrong. If you force or manipulate people to behave against their better judgement in this way, many of them will end up in a mess. Of course, it is not politic for military psychologists 鈥� and others in government employ 鈥� to say so.
There is no easy post hoc solution to helping those who suffer psychological difficulties following active service, but it would go a long way to help if governments and society acknowledged the injustice of using propaganda on their impressionable youth to direct them towards fighting for unjust and immoral purposes.
Energy generation
Your recent article on the asserts that “only big projects can deliver big quantities of renewable energy” (18 April, p 32). A big project with less environmental impact than this tidal barrage would be installing solar panels on every roof in the UK.
If energy companies were allowed to install and own micro-generation facilities at or near the point of energy consumption then several issues are addressed by a single measure. No unspoilt land is exploited, power distribution networks can be reduced, and the investment and maintenance costs of micro-generation are not borne by individuals. In addition, greater interaction with production may encourage homeowners to reduce their energy consumption.
From Alan Luff
What seems to be missed in the arguments about the possible Severn barrage is that those who oppose it are going to lose out anyway. If there is a full barrage they will lose their mudflats. If we fail to take on climate change with the biggest schemes possible, sea levels will rise 鈥� and they will lose their mudflats.
Cardiff, UK
Off the rails
You map railways in your article on the remotest places on Earth, saying “they are confined mainly to the richer nations of Europe, the US, Australia and Japan” (18 April, p 40).
What puzzles me is that you omit Canada, yet include Australia. A list of railways accessing remote regions should make mention of Canada, where the railway plays an essential role 鈥� as it does in our smaller cousin, Australia.
While part of North America, Canada is not in the US. We’re too big 鈥� and too rich, for that matter 鈥� to be ignored.
From David Garnett
In the 1800s, it took months for news of Australia to reach Europe. It now appears to be taking years.
In your review of our modern, hyperconnected world, you show the rail link from Adelaide to the north terminating at Alice Springs. The line runs across the continent from Adelaide to Darwin and has been carrying freight and passengers since 15 January 2004.
Darwin, Northern Territory, Australia
The editor writes:
鈥� The researchers at the European Commission’s and the based their map on from 1997. The construction of the Alice Springs to Darwin section of The Ghan railway started in 2001.
All or nothing
Bob Holmes suggests that the bacterium Syntrophus would produce pure hydrogen for us, were it not for its attendant methanogenic archaebacteria, which convert the hydrogen into methane (18 April, p 8). In fact, Syntrophus would not grow at all in isolation 鈥� and the name reflects this.
Syntrophus and the archaebacteria work by : the former is able to produce hydrogen only as long as the latter maintain a virtually zero concentration of hydrogen around it. Break the link and it becomes thermodynamically impossible for the hydrogen to be generated.
Gobbledegookae
In your Feedback item regarding the website of energy company EDF, you said that the dummy text “‘Lorem ipsum…’ looks as if it means something, but doesn’t” (2 May).
Contrary to popular belief, Lorem Ipsum, which has been the printing industry’s standard dummy text for hundreds of years, is not random text. It originates from a piece }of Latin literature De Finibus Bonorum et Malorum (The Extremes of Good and Evil) by Cicero.
The editor writes:
鈥� The text of Lorem Ipsum is a mangled version of the original Latin. While some of the words have meaning, the overall text as it usually appears does not make sense. This is in part why it has long been the standard fill-text used by typesetters.
For the record
鈥� Let’s be clear: the rate at which sunlight delivers energy to the Earth’s surface should be expressed in terawatts. Our “For the record” of 25 April (p 25) not only contained a nonsense of its own (suggesting that a terawatt is different from a terajoule per second), but also failed to address our original blooper, in which we referred to terawatts per day (4 April, p 24).