Best, G.

Christensen, John M.

Online Research Database In Technology

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New and emerging bioenergy technologiesPublication date:2003Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Best, G., & Christensen, J. M. (2003). Role of biomass in global energy supply. In H. Larsen, J. Kossmann, & L.Sønderberg Petersen (Eds.), Risø energy report 2. New and emerging bioenergy technologies (pp. 8-12).(Denmark. Forskningscenter Risoe. Risoe-R; No. 1430(EN)).3Risø Energy Report 2Bioenergy resources: an introductionBioenergy is energy of biological and renewable origin,normally in the form of purpose-grown energy crops orby-products from agriculture, forestry or fisheries. Exam-ples of bioenergy resources are fuel wood, charcoal, sugarbagasse, sweet sorghum stocks, livestock manure, biogas,microbial biomass and algae.Biomass provides approximately 11–14% of the world’senergy (IEA, UNDP, WEC), but there are significant dif-ferences between industrialised and developing coun-tries.In many developing countries biomass is the mostimportant energy source. As a global average, biomassprovides approximately 35% of developing countries’energy (WEC, UNDP), but there are large regional differ-ences. Many sub-Saharan African countries, for instance,depend on biomass for up to 90% of their energy, indi-cating that they have little in the way of industry orother modern activities.The main sources of biomass in developing countries aretraditional wood fuels, either collected and used in anon-commercial way or bought in local markets as fire-wood or charcoal.In industrialised countries, biofuels have for a long timebeen considered as old-fashioned because of their bulkynature and low energy content compared to fossil fuels.In the last decade, however, interest in bioenergy hasincreased. Reasons for this include:• Growing concern about climate change – biofuels canbe carbon-neutral if they are produced in a sustainableway;• Technological advances in biomass conversion, com-bined with significant changes in energy markets;• Biofuels have the unique characteristic of being theonly sources of renewable energy that are available ingaseous, liquid and solid states;• Increasing focus on security of energy supply; and• Increasing interest in renewable energy generally.So while many developing countries will aim at reducingdependence on traditional bioenergy fuels as part of poli-cies to improve access to modern energy services, theglobal trend is expected to focus on how to increase theshare of modern bioenergy in the global energy mix.Examples of current bioenergy use in industrialisedcountries are the USA (4%), Sweden (17%) and Finland(20%) (WEC). Data on bioenergy resources and utilisa-tion is generally uncertain because of the very diverseand dispersed nature of the resources. In most statistics,bioenergy resources are usually classified as either animalmanure or plant biomass, the latter including municipaland other solid waste.Bioenergy could in principle provide all the world’senergy requirements, but its real technical and economicpotential is much lower. The WEC Survey of EnergyResources (WEC 2001) estimates that bioenergy couldtheoretically provide 2900 EJ/y, but that technical andeconomic factors limit its current practical potential tojust 270 EJ/y. Current use of bioenergy is estimated ataround 55 EJ/y.Figure 2 shows the potential and current use of bio-energy by region, based on data from Kaltschmitt. Evenwith the current resource base, it is clear that the practi-Role of biomass in global energy supplyGUSTAVO BEST, FAO, ROME & JOHN CHRISTENSEN, RISØ NATIONAL LABORATORYRole of biomass in global energy supply8Table 1. Types of plant biomass. Source: UNDP, 2000.Woody biomass Non-woody biomass Processed waste Processed fuelsTrees Energy crops such as sugar cane Cereal husks and cobs Charcoal (wood and residues)Shrubs and scrub Cereal straw Bagasse Briquetted or densified biomassBushes such as coffee and tea Cotton, cassava, tobacco stems Wastes from pineapple and Methanol and ethanoland roots (partly woody) other fruits (wood alcohol)Sweepings from forest floor Grass Plant oil cake Plant oils such as palm, rapeseed (canola) and sunflowerBamboo Bananas and plantains Sawmill wastes Producer gasPalms Soft stems, such as those of Industrial wood bark and Biogaspulses and potatoes logging wastesSwamp and water plants Black liquor from pulp millsMunicipal waste3Risø Energy Report 2cal potential of bioenergy is much greater than its cur-rent exploitation. Obstacles to greater use of bioenergyinclude poor matching between demand and resources,and high costs compared to other energy sources.Projections by the WEC, WEA and IPCC estimate that by2050 bioenergy could supply a maximum of 250–450EJ/y, representing around a quarter of global final energydemand. This is consistent with Figure 2, which puts thetechnological potential of bioenergy at 25–30% of globalenergy demand. Land availabilityGrowing biomass for energy production on a significantscale consumes both land and labour. Land use inparticular is a key issue in the production of bioenergyresources, because using land for energy crops meansthat less land is available to grow food.It is imperative to ensure that sufficient cropland is avail-able to produce food for the world's expanding popula-tion, taking into consideration that biomass energy canhelp enhance development and food production.Studies by the FAO and others point to significantreserves of potential cropland, but these resources arenot distributed where they will be needed most if presentpredictions about population growth and competitionfor land use hold true.In the industrialised countries, much of the land beingremoved from agricultural production could profitablyand responsibly be used for energy production, becauseof the associated benefits of such land use. The EC's "set-aside" policy, which encourages farmers to keep part oftheir land fallow, and similar schemes in other countriessuch as the US are making significant areas of land avail-able. Growing biomass crops on this land could help tore-invigorate rural economies, as well as providing bioen-ergy and its associated environmental benefits.In the non-industrialised world, land availability variesbetween regions and between countries. Some Asiancountries appear to have no, or almost no, spare landthat could be used for bioenergy. Even in these countries,however, strategies such as agroforestry, efficient energyconversion technologies and the use of agriculturalwastes could create significant amounts of bioenergy.Latin America, much of Africa, and several forest-richcountries in Asia have large areas which could be used forbioenergy, given the right long-term policies.In many developing countries, food and fuel productioncan be integrated in complementary land use systems. Infact, at the small to medium scale (100 kW–1 MW), agri-cultural residues and non-arable land can supply vil-lagers’ energy needs for domestic water, irrigation, light-ing and cooking. Irrigation can greatly increase cropyields, so the implication is that at this scale the use ofindigenous biofuels does not need to consume extra landresources. The production of excess biomass can be con-verted to higher value energy products e.g. charcoal,electricity or synthetic biofuels, which can be sold on theopen market. Firewood and charcoal are already signifi-cant income sources in rural areas.At the larger MW scale, land use conflicts could occurwhere dedicated energy plantations are to supply a cen-tral conversion facility i.e. where a bioenergy market isRole of biomass in global energy supply 90102030405060708090100n Use/PEC   n Potential/PEC   North-AmericaBioenergy use and potential as (%) of PECLatin-America &CaribbeanNorth-America Africa Europe Former USSR Average195143Figure 2. Technical potential and use of biomass as a percentage of primary energy consumption (PEC) from fossil fuels + hydropower (Based on datafrom Kaltschmitt 2001).3Risø Energy Report 2stimulated. Since biomass is a low energy density fuel,high transport costs require that the conversion facilitysecure supplies from as close to the plant as possible.Thus, measures to protect the small farmer near to sucha plant may be necessary. However, concerns must alsobe measured against the benefits accrued by such a planti.e. increased rural employment (at all skill levels), asecure market for agricultural products and the provisionof cheap indigenous supplies of energy.Bioenergy production can be a way to rehabilitatemarginal and degraded land and bring it back into prof-itable use. This will only happen, however, if it is sup-ported by policy. Without such policy, there is a dangerthat bioenergy producers will seek good land, whereyields are higher, and so compete directly with food pro-duction.Water restrictionsOne in five developing countries will face water short-ages by 2030. The biggest consumer of water is agricul-ture, which accounts for around 70% of all freshwaterwithdrawals worldwide. With a growing world popula-tion, agriculture will face more competition from indus-trial and domestic water users. As a result, agriculture willhave to use water more efficiently.Figure 3 shows agricultural water withdrawals by regionas a percentage of water available, and so indicates thelevel of “stress” caused by current agricultural practices.If bioenergy resources are to meet their full potential,they will have to match the water consumption of othercrops in the same region.Wood, the traditional fuelLack of access to convenient and efficient energy is amajor barrier to achieving meaningful and long-lastingsolutions to poverty. Access to energy is essential in alle-viating poverty and achieving sustainable developmentgoals, because it supports strategies for improvingemployment, education, water supply, public health,local self-sufficiency and a host of other developmentbenefits.Fuel wood and charcoal are the dominant sources ofenergy for about half the world’s population. In manycountries they also constitute the major forest products.Two to three billion people rely on wood for their pri-mary energy needs and to provide a wide range of otheressential goods and services.For many of these people, wood is far from being a cleanand efficient energy source, it is simply their only afford-able option. Compared to conventional fossil fuels,wood-fuel and charcoal have low calorific values and aredifficult to handle, expensive to transport over long dis-tances and considered dirty in most residential contexts.In many cases, the harvesting of wood-fuels also causesdeforestation and loss of vegetation cover.These negative perceptions are not easily changed, andthey restrict the options open to policymakers. This isdespite the fact that several countries, both industri-alised and developing, have shown that many of thedrawbacks can be overcome by using the right techno-logy.In fact, it is often not understood that appropriate wood-based energy systems can contribute significantly to sus-Role of biomass in global energy supply10Figure 3. Agricultural water withdrawals: FAO (2003): Agriculture, food and water. A contribution to the World Water Development report. FAO, Rome 3Risø Energy Report 2tainable development, particularly in the poorer areas ofdeveloping countries. Wood fuels have some advantagesover other energy sources:• They contribute to poverty reduction in developingcountries;• They meet energy needs at all times, without expensiveconversion devices;• They can deliver energy in all the forms that peopleneed (liquid and gaseous fuels, heat and electricity);• They are CO2-neutral, and can even act as carbon sinks;and• They help to restore unproductive and degraded lands,increasing biodiversity, soil fertility and water reten-tion.Wood fuels usually form part of larger multi purpose sys-tems within forests or agricultural areas. These systemsalso provide non-wood forest products, reservoirs of bio-diversity, traditional medicines and shelter from thewind and sun, all at little or no cost to the world’s poor-est people. Moreover, most of the added value from vil-lage-scale bioenergy systems is retained locally and helpsto reduce poverty.But although wood fuels are widely available and afford-able in rural areas of most developing countries, manyresources still remain untapped. For wood energy to ful-fil its potential as an instrument for sustainable develop-ment, a series of technological, institutional, economicand social challenges need to be addressed.Fuel of the FutureWith the traditional association of bioenergy as old fash-ioned and for the poor, the recent interest in biomassresources has invented a new term “modern bioenergy”which covers a number of technological areas from com-bustion at domestic, industrial or power plant scale, gasi-fication, hydrolysis, pyrolysis, extraction, digestion etc. Most of these technologies have been available fordecades but recent advances in performance have madethem economically interesting in view of the resourcepotential and the possibility of improving environmen-tal performance often along with local employmentopportunities. Details concerning individual bioenergyconversion technologies are presented in chapter 5.Driving forces and practical limitationsTwo trends emerge from the discussions above:a. Developing countries will in general aim to reducetheir dependence on traditional bioenergy as part oftheir development strategies. The relative share ofbioenergy in the energy balance will therefore godown, though the number of people depending ontraditional bioenergy will probably remain constant,with corresponding consequences for health andresources.b. Industrialised countries, plus a number of developingcountries, will aim to increase their use of modernbioenergy technologies.Practical limits to bioenergy expansionPractical limits to bioenergy expansion are set by factorsincluding:• Resource potential and distribution (as discussed in theIntroduction);• Technological development state of the biomass con-version technologies;• Costs of technologies and resources;• Lack of social and organisational structures for fuel sup-ply;• Public acceptability; and• Land-use and environmental aspects.Most of these barriers to the increased use of bioenergycan be overcome through dedicated interventions byboth public- and private-sector entities, focusing on:• Developing and deploying cost-effective conversiontechnologies;• Developing and implementing improved dedicatedbioenergy crop production systems;• Establishing bioenergy markets and organisationalstructures to transport and deliver bioenergy resourcesand products; and• Valuing the environmental benefits to society, such ason the carbon balance.Driving forces to support these activities will be:• Security of energy supply, which can be increased byusing domestic resources;• Employment and land-use aspects (both for andagainst the increased use of biofuels);• Global concerns about climate change; and• Local concerns about health issues related to burningbiofuels indoors.All of these driving forces in support of biofuels requiretargeted policy interventions to ensure that the socialbenefits of increased bioenergy use are properly reflectedin the energy markets. In some cases “smart” subsidyschemes may even be needed to ensure that new bioen-ergy resources and technologies get a level playing fieldin established energy markets.A concrete example of a large-scale bioenergy pro-gramme is Brazil’s PRO-ALCOOL, in which ethanol fromsugar cane bagasse is used as a transport fuel. In 1999Brazil produced and used about 13 billion litres ofethanol in this way (UNDP, 2000).The PRO-ALCOOL programme was launched in 1975 asa response to the oil crises. In spite of mixed economicresults it has been a technical success, and has providedboth social and environmental benefits.The cost of producing the ethanol is equivalent to an oilprice of around USD 30 per barrel. When oil prices areRole of biomass in global energy supply 113Risø Energy Report 2below this level, the country must pay to produce fuelthat could be imported more cheaply as oil.The beneficial effects of lowering imports by USD 20–30billion, creating (directly and indirectly) almost a millionjobs, cutting air pollution in urban areas and reducingenergy-related carbon emissions by 15–20% can be offsetagainst this.Specific national circumstances mean that it may not bepossible to replicate the Brazilian example directly. ThePRO-ALCOOL programme does show, however, thatgood policymaking in response to the driving forcesmentioned above can create effective bioenergy solu-tions. The programme has contributed significantly toovercoming the technological barriers to the wider use ofethanol, not just in Brazil but also worldwide.Role of biomass in global energy supply12

Role of biomass in global energy supply

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Role of biomass in global energy supply

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