Dernière mise à jour : 6 nov. 2019
If you listen to the clamor of the news media and the climate change activists you may think that the most effective ways to reduce carbon emission would be to buy an electric car and stop eating meat! But, as with so many things, there is a lot of emotional mumbo jumbo going on here. Some of the less “exciting” aspects of our conventional lives also produce significant quantities of CO2 but they are scarcely even mentioned. And there is complete confusion about the relative importance of methane and carbon dioxide.
Let's have a closer look at meat and methane. The first thing we have to understand is that methane and carbon dioxide behave completely differently in the atmosphere, Methane is degraded quite quickly (about 8 years) into carbon dioxide which exactly matches the carbon dioxide which was taken from the atmosphere when the animals' food was growing. This means, for example, that if you had 10,000 dairy cattle producing methane for 100 years the net increase in atmospheric methane would be zero. This is quite different from adding carbon dioxide to the atmosphere by burning fossil fuels. Ruminants do not mine carbon, they borrow it from the atmosphere.
In general terms the methane in our atmosphere produces about one quarter of global warming. Livestock produce about 17 percent of this methane (about 90m tons) Wetlands, termites and the oceans produce about 190m tons. The rest is man made from biofuels, landfill, fuel production biomass burning and rice farming. Altogether ruminant methane is responsible for just 4 percent of global warming – not a greatly significant quantity.
Now let's turn to the strange attraction of electric cars! They are certainly not “pollution free” as stated on stickers sometimes seen ostentatiously displayed on rear windows. Their pollution takes place first at the central thermal generating station and second when their toxic lithium batteries are dumped in landfill after they have been used! Yes – it's really true. Humans are burying the scarce and vital metal which is lithium in landfill because it's cheaper to mine more than to re-process the complex batteries. (Note that lithium is also likely to be a vital fuel for nuclear fusion when humans finally perfect this process.) Future generations will see this as absolute madness!
So what's going on at our power stations? At present about two thirds of our electrical energy is produced by thermal power stations – burning fossil fuels (either gas or coal). Thermal power stations are very inefficient users of energy because the basic requirements of thermo-dynamics prevent them converting more than 34 percent of the thermal energy into electicity. And a further 10 percent is lost down the transmission lines. This efficiency compares very badly with the efficiency of a modern diesel engine which can convert more than 50 percent of its thermal energy into power. So it's plain to see that if a diesel car can travel 40 miles on one gallon of fuel then travelling the same distance in an electric car would require burning almost one and a half gallons of fuel at the power station (even discounting the contribution of renewables). The electric car's production of carbon dioxide is almost 50 percent greater than a diesel car. Our dependence on centrally generated electricity is the single most wasteful use of fossil fuels – local generation using internal combustion engines would enable huge reductions in release of carbon dioxide.
There are two other major sources producing greenhouse gases which are “hidden in plain sight” - never mentioned by activists or green parties. One is our use of the flush toilet and treatment of the associated water-borne sewage. The other is our sloppy habit of putting organic waste into our rubbish so it ends up (about 10 million tons annually in the UK) in landfill. It is not easy to find reliable figures for the energy required to collect, purify and pump clean water to every household, nor is it easy to find estimates of the energy required to pump away the sewage, treat it and process the waste (in the UK we still dump around 1 million tons of sewage sludge onto farmland every year). The figures seem to vary from between 15 KwH to 1.5 KwH per gallon. The average person flushes away about 10 gallons of waste each day so even if we take the lowest figure this means our inefficient central power stations must burn about 5 Kg of oil to power our daily use of the flush toilet – burning 5Kg of oil produces 15 Kg of carbon dioxide (a figure very similar to driving a conventional car about 40 miles. On this basis each toilet flush produces almost the same carbon footprint as driving your car 10 miles – and, as a nation, we make around 90 billion toilet flushes every year! (Note that our flush toilets are also steadily transferring important plant nutrients in our diet from the land into our rivers, lakes and seas.)
Finally let's realize that the elimination of methane from organic waste in landfill probably requires the easiest of all policy changes. Methane (which may or may not be used in power production) is created when organic waste decays anaerobically underground (in the absence of oxygen). All households should be required to separate their organic waste and either compost it aerobically at home or pass it on to the local authority for proper composting or biodigestion. Generally the UK is miles behind other countries (particularly Germany and China) in use of biodigesters to process sewage and organic waste. At one and the same time this eliminates pollution and provides “renewable” electricity from burning the methane they produce in local electricity generators.
The final comment which is worth making is that planting trees is a win/win policy as far as reducing carbon in the global atmosphere. Every mature tree collects about 50lb of carbon from the air each year. The UK has about 4 billion trees at present – they collect about 100 million tons of carbon dioxide each year.
If we planted another 12 billion trees we would not only greatly enhance the natural landscape, we would become one of the first nations making zero net carbon emissions!