Biomass energy

Second in current importance as a renewable energy source is the use of bio-mass.37 The annual global primary production of biomass of all kinds expressed in energy units is about 4500 EJ (= 107 Gtoe). About 1% of this is currently turned into energy mostly in developing countries - we have labelled it 'traditional biomass'. It has been estimated that about 6% of the total could become available from energy crops taking into account the economics of production and the availability of suitable land.38 The energy so generated would represent about 75% of current world energy consumption, so in principle a large contribution from biomass could be made towards global energy needs. It is a genuinely renewable resource in that the carbon dioxide that is emitted when the biomass is burnt is turned back into carbon, through the process of photosynthesis, in the renewed biomass when it is grown again. The word biomass not only covers crops of all kinds but also domestic, industrial and agricultural dry waste material and wet waste material, all of which can be used as fuel for heating and to power electricity generators; some are also appropriate to use for the manufacture of liquid or gaseous fuels (see next section). Since biomass is widely distributed, it is particularly appropriate as a distributed energy source suitable for rural areas. For instance, in Upper Austria, with a population of 1.5 million, in 2003 14% of their total energy came from local biomass - planned to increase to 30% by 2010 and to continue to grow substantially thereafter.

In much of the developing world, most of the population live in areas where there is no access to modern or on-grid energy. They rely on 'traditional biomass' (fuelwood, dung, rice husks and other forms of biomass) to satisfy their needs for cooking and heating. About 10% of world energy originates from these sources, supplying over one-third of the world's population. Although these sources are in principle renewable, it is still important that they are employed efficiently, and a great deal of room for increased efficiency exists. For instance, a large proportion of each day is often spent in collecting firewood especially by the women, increasingly far afield from their homes.

The burning of biomass in homes causes serious health problems and has been identified by the World Health Organization as one of the most serious causes of illness and mortality especially amongst children. For instance, much cooking is still carried out on open fires with their associated indoor pollution and where only about 5% of the heat reaches the inside of the cooking pot. The introduction of a simple stove can increase this to 20% or with a little elaboration to 50%.39 An urgent need exists for the large-scale provision of stoves using simple technology that is sustainable - although there is often considerable consumer resistance to their introduction. Other means of reducing fuelwood demand are to encourage alternatives such as the use of fuel from crop wastes, of methane from sewage or other waste material, or of solar cookers (mentioned again later on). From the existing consumption of 'traditional biomass' there is the potential to produce sustainable 'modern' energy services with much greater efficiency and much less pollution for the 2 billion or so people who currently rely on this basic energy source. A particular challenge is to set up appropriate management and infrastructure for the provision of these services in rural areas in developing countries (see box below).

Consider for instance the use of waste.40 There is considerable public awareness of the vast amount of waste produced in modern society. The UK, for example, produces each year somewhat over 30 million tonnes of domestic solid waste, or about half a tonne for every citizen - a typical value for a country in the developed world. Even with major programmes for recycling some of it, large quantities would still remain. If it were all incinerated for power generation (modern technology enables this to be done with negligible air pollution) nearly 2 GW could be generated, about 5% of the UK's electricity requirement.41 Uppsala in Sweden is an example of a city with a comprehensive district heating system, for which, before 1980, over 90% of the energy was provided from oil. A decision was then made to move to renewable energy and by 1993 energy from waste incineration and from other biomass fuel sources provided nearly 80% of what is required for the city's heating.

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