Biomass resource facilities and biomass conversion processing for fuels and chemicals
Ayhan Demirbas ß*
P.K.216,TR-61035-Trabzon,Turkey
Received 19April 2000;accepted 28September 2000
Abstract
Biomass resources include wood and wood wastes,agricultural crops and their waste byproducts,mu-nicipal solid waste,animal wastes,waste from food processing and aquatic plants and algae.Biomass is ud to meet a variety of energy needs,including generating electricity,heating homes,fueling vehicles and providing process heat for industrial facilities.The conversion technologies for utilizing biomass can be parated into four basic categories:direct combustion process,thermochemical process,biochemical process and agrochemical process.Thermochemical conversion process can be subdivided into gas-i®cation,pyrolysis,supercritical ¯uid extraction and direct liquefaction.Pyrolysis is the thermochemical process that converts biomass into liquid,charcoal and non-condensable gas,acetic acid,acetone and methanol by heating the biomass to about 750K in the
abnce of air.If the purpo is to maximize the yield of liquid products resulting from biomass pyrolysis,a low temperature,high heating rate,short gas residence time process would be required.For high char production,a low temperature,low heating rate process would be chon.If the purpo is to maximize the yield of fuel gas resulting from pyrolysis,a high temperature,low heating rate,long gas residence time process would be preferred.Ó2001Elvier Science Ltd.All rights rerved.
Keywords:Biomass;Biomass resource facilities;Biomass conversion products;Pyrolysis
1.Introduction
There are many di erent ways in which the abundance of energy around us can be stored,converted and ampli®ed for our u.Energy sources will play an important role in the
world's Energy Conversion and Management 42(2001)
1357±/locate/enconman
*Tel.:+90-0462-248-7429;fax:+90-0462-248-7344.E-mail address: (A.Demirbas ß).
鲫鱼饵料配方0196-8904/01/$-e front matter Ó2001Elvier Science Ltd.All rights rerved.PII:S0196-8904(00)00137-0
1358 A.Demirba sß/Energy Conversion and Management42(2001)1357±1378
future.The energy sources have been split into three categories:fossil fuels,renewable sources and nuclear sources.The fossil fuels are coal,petroleum and natural gas.
The point where the cost of producing energy from fossil fuels exceeds the cost of biomass fuels has been reached.With a few exceptions,energy from fossil fuels will cost more money than the same amount of energy supplied through biomass conversion.Biomass is the term ud to de-scribe all biologically produced matter.World production of biomass is estimated at146billion metric tons a year,mostly wild plant growth[1].
The renewable energy sources are solar,wind,hydroelectric,biomass and geothermal power. The nuclear powered sources are®ssion and fusion.
小朋友生日祝福Biomass is the name given to all the earth's living matter.It is a general term for material derived from growing plants or from animal manure(which is e ectively a procesd form of plant material).It is a rather simple term for all organic material that stems from plants(including algae),trees and crops.Biomass energy is derived from plant and animal material,such as wood from natural forests,waste from agricultural and forestry process and industrial,human or animal wastes.
Plants absorb solar energy,using it to drive the process of photosynthesis,which enables them to live.The energy in biomass from plant matter originally comes from solar energy through the process known as photosynthesis.The energy,which is stored in plants and animals (that eat plants or other animals),or in the wastes that they produce,is called biomass energy. This energy can be recovered by burning biomass as a fuel.During combustion,biomass re-leas heat and carbon dioxide that was absorbed while the plant was growing.Esntially,the u of biomass is the reversal of photosynthesis.Is biomass energy a variety of chemical energy? In nature,all biomass ultimately decompos to its molecules with the relea of heat.The relea of energy from the combustion of biomass imitates natural process.Therefore,the energy obtained from biomass is a form of renewable energy and,in principle,utilizing this energy does not add carbon dioxide to the environment,in contrast to fossil fuels[2].Of all the renewable sources of energy,biomass is unique in
that it is e ectively stored solar energy. Furthermore,it is the only renewable source of carbon and is able to be converted into con-venient solid,liquid and gaous fuels[3].
Biomass can be ud burning wood for heating and cooking)or indirectly by converting it into a liquid or gaous alcohol from sugar crops or biogas from animal waste).The net energy available from biomass when it is combusted ranges from about8MJ/kg for green wood,to20MJ/kg for dry plant matter[4,5],to55MJ/kg for methane,as compared with about27MJ/kg for coal[2].
Many biomass®red electricity generators u waste materials,such as straw or domestic refu. Other schemes are bad on the idea of cultivating crops of various kinds,especially to provide biomass for fuel.
2.How important is biomass?
Biomass,mainly in the form of wood,is the oldest form of energy ud by humans.Tra-ditionally,biomass has been utilized through direct combustion,and this process is still widely
A.Demirba sß/Energy Conversion and Management42(2001)1357±13781359 ud in many parts of
the world.Biomass has historically been a disperd,labor intensive and land intensive source of energy.Therefore,as industrial activity has incread in countries,more concentrated and convenient sources of energy have been substituted for bio-mass.
Biomass,mainly,now reprents only3%of primary energy consumption in industrialized countries[6].However,much of the rural population in developing countries,which reprents about50%of the world's population,is reliant on biomass,mainly in the form of wood,for fuel. Biomass accounts for35%of primary energy consumption in developing countries,raising the world total to14%of primary energy consumption[6].
The earth's natural biomass replacement reprents an energy supply of around3000EJ (3Â1021J)a year,of which just under2%is currently(1998)ud as fuel.It is not possible, however,to u all of the annual production of biomass in a sustainable manner.One analysis provided by the United Nations Conference on Environment and Development(UNCED)esti-mates that biomass could potentially supply about half of the prent world primary energy consumption by the year2050[6].
Biomass has great potential as a renewable energy source,both for the richer countries and for the developing world.Biomass as a fuel is still in the experimental stage and provides only about
0.25%of the total electricity generating capacity in the UK.However,this is likely to increa for
a number of reasons.One reason is that European and UK legislation aims to encourage less polluting methods of waste disposal,and one viable option is to burn the waste to generate power. Another reason is that biomass power systems will become more a ordable as the technology improves.
Biomass is ud in a similar way to fossil fuels,by burning it at a constant rate in a boiler furnace to heat water and produce steam.Pipes carry the steam through the furnace again to rai its temperature and pressure further,and then,it pass through the multiple blades of a turbine, spinning the shaft.The turbine shaft drives an electricity generator which produces an alternating current for u locally or to supply the national grid.
Liquid biofuels,such as wheat,sugar,root,rapeed and sun¯ower oil,are currently being ud in some member states of the European Union,like Austria,Belgium,France,Germany,Italy and Spain[7].
Refu fuels ud in power stations would otherwi have to be dispod of in land®ll sites or in some other way.E cient burning reduces them to a relatively small volume of ash while also producin
震上艮下g uful electricity or heat energy.
There are also potential bene®ts in growing biomass especially for fuel.Provided the right crops are chon,it is possible to u poor quality land which is unsuitable for growing food.
Burning biomass produces some pollutants,including dust and the acid rain gas sulfur di-oxide(SO2)and nitrogen oxides(NO x).Burning wood produces90%less sulfur than coal.The can all be reduced before releasing the fuel gas into the atmosphere.At the prent rate of u, the quantities of atmospheric pollution involved are insigni®cant compared with other pollution sources,but this would be a factor to consider if the u of biomass incread.
Carbon dioxide(CO2),the greenhou gas,is also relead.However,as this originates from harvested or procesd plants,which have absorbed it from the atmosphere in the®rst place,no additional amounts are involved.
1360 A.Demirba sß/Energy Conversion and Management42(2001)1357±1378
3.Biomass energy
Biomass energy is one of humanity's earliest sources of energy.Biomass is ud to meet a variety of
energy needs,including generating electricity,heating homes,fueling vehicles and providing process heat for industrial facilities.Biomass potential includes wood and animal and plant wastes.Biomass is only an organic petroleum substitute which is renewable.The term ÔbiomassÕrefers to forestry,purpoly grown agricultural crops,trees and plants and organic, agricultural,agro-industrial and domestic wastes(municipal and solid waste)[8].Biomass is the name given to the plant matter which is created by photosynthesis in which the sun's energy converts water and CO2into organic matter.Thus,biomass materials are directly or indirectly a result of plant growth.The include®rewood plantations,agricultural residues,forestry residues, animal wastes etc.Fossil fuels can also be termed biomass,since they are the fossilized remains of plants that grew some millions of years ago.
The one renewable energy source on which mankind has relied since the discovery of®re is photosynthesis,the process in which solar energy is converted into an energy rich biomass.In this process,solar energy,absorbed by green plant tissue,provides energy to reduce CO2and form carbohydrates which are then utilized as energy sources and raw materials for all other synthetic reactions in the plant.Thus,solar energy is captured and stored in the plant,thereby providing food,®ber,fuel and shelter for mankind.However,this photosynthesis us only a small portion of the
sun's energy to®x200billion tons of carbon into terrestrial and aquatic biomass with an energy content of3000billion GJ/y.Yet,only1/10th of the worldÕs biomass energy is consumed,while the rest is left untapped[9].Every year,plants store10times the prent annual consumption of energy. This large quantity of energy can not only contribute to the country's energy resources but also can e ectively provide a wide range of chemical feed stocks for the organic chemical industry,thus saving the consumption of precious non-renewable petroleum products.Moreover,it is environ-mentally friendly and prevents ecological imbalance.Stored plant energy can be utilized by burning it directly or using various process to obtain potential fuels,such as ethanol,methane etc. Forest energy involves the u of forest biomass which is currently not being ud in the tra-ditional forest products industries.Esntially,this means the forest residues left after forest harvesting,residual trees and scrub or under-managed wood land.Forest residues alone count for some50%of the total forest biomass and are currently left in the forest to rot[10].
The opportunity to combine fuelwood production with e uent disposal has many potential environmental bene®ts.The economic feasibility of woody biomass plantations is di cult to justify at prent,but if full costing of externalities,such as CO2emissions,are to be applied in the future,then acceptable payback periods for boiler conversions and handling and storage facilities could be achieved.
4.Resources of biomass
Biomass resources include wood and wood wastes,agricultural crops and their waste by-products,municipal solid waste(MSW),animal wastes,waste from food processing and aquatic plants and algae.The average majority of biomass energy is produced from wood and wood wastes(64%),followed by MSW(24%),agricultural waste(5%)and land®ll gas(5%)[7].
猫背影
A.Demirba sß/Energy Conversion and Management42(2001)1357±13781361 Biomass is the oldest known source of energy.Biomass is a renewable source.It supplies only 4%of the industrialized countries'energy.Biomass energy comes from burning organic matter. Biomass is burned in a special waste to energy plant to produce electricity.Biomass fuel comes from land®lls and agricultural waste.In land®lls,a gas called methane is ud as a fuel in waste to energy plants.Energy from biomass costs more than coal.Burning waste for energy reduces60±90%of the trash dumped in land®lls.This also reduces land®ll cost.
临海江南长城
Biomass di ers from other alternative energy sources in that the resource is varied,and it can be converted to energy through many conversion process.Biomass resources can be divided into three general categories:
1.wastes
2.standing forests
< crops
Biomass resources that can be ud for energy production cover a wide range of materials. Biomass energy can be parated into two categories,namely modern biomass and traditional biomass.Modern biomass usually involves large scale us and aims to substitute for conventional energy sources.It includes wood and agricultural residues,urban wastes and biofuels,such as biogas and energy crops.Traditional biomass is generally con®ned to developing countries and small scale us.It includes fuelwood and charcoal for domestic u,rice husks and other plant residues and animal wastes.Examples of biomass energy resources are:
Wastes:
·agricultural production wastes
·agricultural processing wastes
·crop residues
·mill wood wastes
·urban wood wastes
·urban organic wastes
Forest products:
·wood
·logging residues
·trees,shrubs and wood residues
·sawdust,bark etc.from forest clearings
Energy crops:
·short rotation woody crops
鸡胗怎么炒·herbaceous woody crops
·
grass
·starch crops(corn,wheat and barley)
·sugar crops(cane and beet)
·forage crops(grass,alfalfa and clover)
·oiled crops(soybeen,sun¯ower,sa ower)
1362 A.Demirba sß/Energy Conversion and Management42(2001)1357±1378
Aquatic plants:
·algae
·water weed
·water hyacinth
·reed and rushes
艺术节英语
The demand for energy is increasing at an exponential rate due to the exponential growth of world population.This,combined with the widespread depletion of fossil fuels and gradually emerging consciousness about environmental degradation,suggests that the energy supply in the future has to come from renewable sources of energy.Statistics show that,although total re-newables now account for nearly18%of global primary energy supply,out of this,over55%is supplied by traditional biomass and about30%by large hydro.Solar,wind,modern biomass, geothermal,small hydro(below10MW)and ocean energy all together account for only12%of total renewables.The new renewables account only for2%of the world primary energy supply. Biomass contributes about12%of today's world primary energy supply,while in many de-veloping countries,its contribution ranges from40%to50%[8].
World production of biomass is estimated at146billion metric tons a year,mostly wild plant growth.Some farm crops and trees can produce up to20metric tons per acre of biomass a year. Types of algae and grass may produce50metric tons per year[1].
For its mission analysis study conducted for the USDepartment of Energy in1979,S tanford Rearch Institute(SRI)cho®ve types of biomass materials to investigate for energy conver-sion:woody plants,herbaceous plants(tho that do not produce persistent woody material), aquatic plants and manure.Herbaceous plants were divided into two categories,tho with low moisture cont
ent and tho with high moisture content[7].
5.Energy from biomass
Biomass is not in ideal form for fuel u.The heat content calculated on a dry mass basis must be corrected for the natural water content that can reduce the net heat available by as much as 20%in direct combustion applications.Gasi®cation to low calori®c gas carries an additional net energy loss,and conversion to synthetic natural gas and liquid fuels results in still greater re-duction of net energy,to perhaps30%of the original heat content[11].
Photosynthesis is a process by which plants u solar energy to transfer the low energy CO2into energy rich organic compounds.Thus,solar energy is captured and stored in the form of chemical energy.
弟子规拼音Wood is still a predominant fuel in many non-OPEC,tropical,developing countries,and it will con-tinue to be so for at least the next40±50years.It competes well with fossil fuels,becau it is re-newable,and with soft energies like solar and wind,on account of its energy storage capacity.It is being ud in the domestic(for cooking and water heating),commercial(water heating)and industrial (for water heating and process heat)ctors and also in rural industries,like brick kilns,potteries etc.
Wood is a composite of cellulo,lignin and hemicellulo(43%,36%and22%,respectively).A typical analysis of dry wood yields carbon(52%),hydrogen(6.3%),oxygen(40.5%)and nitrogen (0.4%).The proximate analysis of wood shows the following components[7]:
