12th International Symposium on District Heating and Cooling

The <strong>12th</strong> <strong>International</strong> <strong>Symposium</strong> on District Heating and Cooling,September 5 th to September 7 th , 2010, Tallinn, EstoniaSystem 1In the current configuration of this system 15-20% ofthe energy demand is covered with fuel oil, whichneeds to be reduced. One interesting option could beto convert biomass into bio oil by pyrolysis and thenuse the bio oil in the existing oil boilers. Bio oil that isnot used within the system can be sold (e.g. summertime). If no pyrolysis reactor is built, a conventionalbiofuel fired combined heat and power plant (bio CHP)will be invested in, building up the reference case.System 2In this system, there is no need for new productionunits, rather there is a high production capacity,allowing for integration of a bioenergy production unit.System 2 has good access to biomass, but might havedifficulties to find a market for large quantities of byproducts.Based on these prerequisites, a suitablecombine technology could be cellulose ethanolproduction with enzymatic hydrolysis aiming at highyield and in-house use of energy by-products.Regarding the O&M cost for the enzymatic process inTable I, future enzyme price are assumed [4], Withtoday‘s prices, the enzymatic process will not beprofitable.System 3In System 3 there is a need for new productioncapacity, which is represented by a bio CHP in thereference case. This system has good access to alarge energy market, which enables output of otherenergy products. Hence, a cellulose ethanol plantbased on acid hydrolysis can complement thereference case investment to build up the combinecase.System 4This system is in many aspects similar to System 3, butethanol production is not in line with company strategy.Moreover, System 3 has good access to peat, whichcould supplement biomass for a large scale productionunit. Hence, gasification of biomass for production ofsynthetic biofuel is evaluated for this system.Environmental evaluationThe assessment of the environmental implication ofintroducing a bioenergy production in an existingdistrict heating system focuses on changes inemissions of green house gases (GHG). A systemapproach for analysing the changes of GHG‘s isapplied. This means that besides changes of the directemissions on site, also the changes of emissions inaffected parts of the energy systems are included; seeFigure 1. For instance, production of biofuel in thecombines ads to the environmental benefit since fossilfuels can be replaced, while reduced electricityproduction has a negative impact to the environmentalbenefit in accordance with marginal electricityproduction.Production,distribution anduse of biomassDirect GHG emissionsGHGDH system withor without bioenergyproductionGHGPowersystemProduction,distribution and useof transportationfuelGHGFig.1. Illustration of the applied system approach forassessing the changes of GHG‘s.In the assessment, all GHG‘s of significance areincluded [3]: carbon dioxide (CO 2 ), dinitrogen oxide(N 2 O) and methane (CH 4 ). For all energy carriers, lifecycle emissions are considered, i.e. both combustionemissions and well-to-gate emissions such asemissions from fuel extraction, processing andtransportation. Also leakages are considered whenapplicable. How the GHG‘s for the relevant energycarriers are assessed are described in brief below, amore thorough description can be found in [3].Theadopted life cycle GHG emissions associated withchanges in consumption/production of the energycarriers are summarized in Table II.Table II. Emission factors for included energy carriers.ENERGY CARRIERBiomass 14-17 1High emission elec. (E1) 800Low emission electricity (E2) 260Pyrolysis oil 292Ethanol 307FT diesel 277Fuel oil 312Biogas 207Pellets 286LIFE CYCLE EMISSION(kg CO 2 eq./MWh)1 The lifecycle emission of biomass is dependent on howthe biomass is used in the energy combines (e.g.hydrolysis for fermentation or gasification)BiomassThe energy input in all four combines is in the form ofbiomass. Production, distribution and use of biomass isrelated to GHG emissions. The GHG emission from theuse of biomass differs depending on how the biomassis used. Combustion raises emissions of both methane145