浏览: 日期:2020-06-10
The use of biomass energy as a wide spread, renewable power source provided with proper knowledge, state control and technological how-to, can change both the earth's environment and our attitude towards alternative power resources. To understand how this can happen, the basics of what biomass energy is and how it works have to be presented. All organic matter, such as agricultural residue, wood and animal waste, energy crops, and methane, is a potential source for biomass energy (http://www.mna.hkr.se/~ene02p10/biomass.htm). Biomass energy can be produced by either growing crops especially for this purpose (i.e. sugarcane, soya bean, corn, sweet potato, maize, willow and eucalyptus trees), or converting organic waste (http://www.inforse.org/europe/dieret/Biomass/biomass.html). The organic matter can be burned to produce heat, like the wood fire of old, or they can produce ethanol or other alcoholic fuels (http://www.mna.hkr.se/~ene02p10/biomass.htm). There are differing opinions between respectable scientific communities and one has to analyze the different arguments for and against the use of biomass energy in order to make an informed decision concerning biomass energy.
There are a number of arguments advocating the use of biomass energy. As we see an increase of the greenhouse effect, the trend is to start using renewable power sources. Because in order for biomass energy to be produced needs only organic matter and no chemical is needed for its production, it qualifies as a clean renewable power source. For these reasons, biomass energy generates far less air emissions than fossil fuels. Methane, a more powerful greenhouse gas, can be used for the production of biomass energy thereby decreasing the methane levels in the atmosphere. Biomass materials are often waste products from existing industrial activities that would otherwise be disposed of--at considerable cost. For example, if you burn unusable waste material such as bark, construction waste and tree clippings, you reduce the pressure to expand local landfill sites while generating useful energy (http://www.canren.gc.ca/tech_appl/index.asp?CaId=2&PgId=62).
Biomass energy decreases the reliance on fossil fuels that may be imported, and whose price therefore is subject to variable economic and/or political issues. Bioenergy has a generally positive impact on the local economy. Biofuels are bulky and have a low-energy density so it is not economical to transport them long distances. As a result, the money spent to purchase biofuels generally remains in the local area (http://www.canren.gc.ca/tech_appl/index.asp?CaId=2&PgId=62). As biomass energy is produced locally, it creates thousands of jobs at a local scale as it is labor intensive to create biomass energy. As such, the production of biomass energy helps revitalize rural communities. Extra income without an investment in special equipment can be derived from the collection of agricultural residues, such as straw or corn stover, or from the removal of dead, diseased or low-quality trees from forests.
However, there are arguments that contradict those above. Scientists found that reforestation would sequester between two and nine times as much carbon over 30 years than would be saved by burning biofuels instead of gasoline. 'You get far more carbon sequestered by planting forests than you avoid emissions by producing biofuels on the same land' says a prominents scientist (http://environment.newscientist.com/article/dn12496-forget-biofuels--burn-oil-and-plant-forests-instead.html). The unsustainable and uncontrolled conversion of natural and even virgin ecosystems into managed energy plantations in order to produce material suitable for biomass energy, can lead to the release of carbon from the soil as a result of the accelerated decay of organic matter. (http://www.ecology.com/archived-links/biomass-energy/index.html). It has been established that since the beginning of farming the soybean in Brazil, seven million hectares of the Amazonian rainforest have been converted into energy plantations. Thus, the concerns that environmentalists have expressed about the destruction of the forests in order to make room for biomass crops, such as maize and sugarcane, have been realized. Says, Renton Righelato of the World Land Trust, a conservation agency that seeks to preserve rainforests, "When you do this, you immediately release between 100 and 200 tonnes of carbon [per hectare]" (http://environment.newscientist.com/article/dn12496-forget-biofuels--burn-oil-and-plant-forests-instead.html). Another by-product of the planting of crops suitable for the production of biomass energy is the loss of biodiversity. Transforming natural ecosystems into energy plantations with a very small number of crops, as few as one, can drastically reduce the biodiversity of a region. Such 'monocultures' lack the balance achieved by a diverse ecosystem, and are susceptible to widespread damage by pests or disease (http://www.ecology.com/archived-links/biomass-energy/index.html).
Another important argument is that there simply may not be enough land to grow energy crops and food crops simultaneously. According to a UK survey, the most productive energy crop in the UK is rapeseed and the average yield is 3-3.5 tons per hectare and one ton of rapeseed produces 415 kg of biodiesel, so every hectare of arable land could provide 1.45 tons of transport fuel. Road transport in the UK consumes 37.6m tons of petroleum products a year (http://www.sovereignty.org.uk/features/eco/fuelines.html). The total hectares needed to be planted in order to produce the biodiesel quantity of equal to 37.6m tons of fossil fuel would be roughly 25.9m hectares. The UK does not have this much arable land. In the case of Brazil, Alexandre Conceicao, a member of the MST (Landless Workers Movement), pointed out the orientation was towards the global market concerning energy crop plantations with no regard to the domestic production of food (http://ipsnews.net/news.asp?idnews=38051). So, there might not be any reliance on foreign fossil fuels, but there may be reliance on foreign food exporters.
There are also arguments against the intended location of future energy crop plantations. There has been the suggestion that by converting arable land in Africa into energy crop plantations, both global warming would be tackled and Africans would be helped. It was said that this strategy, "provides a sustainable development path for the many African countries that can produce biofuels cheaply" (http://www.sovereignty.org.uk/features/eco/fuelines.html). Although palm oil can produce four times as much biodiesel per hectare as rapeseed and is grown in places where labor is cheap, planting it is already one of the world's major causes of tropical forest destruction (http://www.sovereignty.org.uk/features/eco/fuelines.html). It is obvious that the production of biomass energy in this manner would entail serious environmental consequences.
The possible creation of jobs has also come under doubt. There have been protests in Brazil about the 'slavery' conditions that the sugar cane plantation workers face. "The social cost of this policy is the overexploitation of labour with an army of seasonal workers who cut one ton of sugar cane for 2.50 reals (1.28 dollars) in precarious conditions which have already caused the deaths of hundreds of workers," says Alexandre Conceicao of the MST (http://ipsnews.net/news.asp?idnews=38051). Camilla Moreno of the Rural University of Rio de Janeiro said that,
the growth of the ethanol industry is breathing life into 'a modern-day version of the sugar plantation slave-labour past,' along with the expansion of a new form of 'ecological imperialism.' Moreno pointed out that large tracts of land have been purchased by international (largely U.S. and European) investment funds, which has brought 'a new form of capitalism that was not familiar to Brazil' (http://ipsnews.net/news.asp?idnews=38051)
The above statements show that not only do the Brazilian people, as a whole, do not benefit from the production of biomass energy, but also that the actual workers are not rewarded properly for their work and work under wretched conditions.