Introduction:Wood is a bio-based material that is declared by IPCC as the sustainable material to encounter climate change and secure global demand1. Wood pellets is very competitive when compared to other fossil fuel as they have same energy content. With EU setting its goal to shift towards a more sustainable energy.The demand for wood pellets has exponentially increased2.
It is assumed that about 42% of energy is obtained from biomass. This energy can be used for heating cooling and electric power generation . 1-refxxxAs wood is high density and can be easily transportable it is more advantageous than other biofuels and as it requires less volume has higher energy content. Some of the inert quality of wood pellet like less moisture content contribute to good transportation quality3.
The European Commission’s Renewable Energy Directive has committed to achieving a 27% share of renewable energy in total energy consumption across its member states by 2030 7.The There has been an increasing interest in and demand for renewable energy globally over the past few decades due to the implementation of various climate change policies and environmental and economic concerns. Biomass are known to have an advantage of storing energy and releasing it when needed in addition to being cheap and light-weighted; a common and widely-used biomass is wood.Wood is a bio-based material that is recognised by the Intergovernmental Panel on Climate Change (IPCC) as a substitute for more energy-intensive materials and a raw material to generate energy; thus making it a sustainable material to encounter climate change and secure global demand. (http://www.ipcc.ch/ipccreports/tar/wg3/index.php?idp=167 Accessed on 19th of January, 2018 at 10:28)Wood pellets are very competitive when compared to other fossil fuel as they have same energy content and therefore can be used for heating, cooling and electricity generation.
They are derived from the pelletisation of wood and wood products like shavings and sawdust. The pelletisation process provides certain benefits like increase in the energy density of the biofuel, reduction in handling, storage and transportation costs and improvement of quality and durability of the biomass; this makes wood pellets a suitable alternative energy source compared to conventional sources like natural gas.The purpose of this study is to assess and understand the environmental implications attached to the production of wood pellets and its use for heating compared to the conventional method of heating via natural gas.
Thus the guiding questions for this study are:What are the contributions of wood pellet as source of heat energy to climate change?How large is the human toxicity effect associated with the production process?Can the emissions involved in the production process be reduced?How high are its impact on ozone depletion? METHOD AND DATA HANDLINGFor the purpose of this study, Life Cycle Assessment is considered the best tool for answering the research questions listed above because LCA is a recognised technique for assessing the environmental impact of a product or service by considering it’s life cycle. It is useful for analysing the various inputs, processes,emissions associated with the production and use of a product while identifying opportunities for quality improvement of the product or service at the various stages involved in its life cycle.For this study, we consider a cradle-to-grave LCA approach which incorporates the production and end use of wood pellets and natural gas.Despite of growing demand for wood pellet production the comprehensive knowledge on the GHG emission . There is a need to perform analysis on the environmental impact of wood pellets on greenhouse gas emissions has to be discussed.
One of the main objectives of this study is to evaluate the environmental impact of wood pellets. Hence we perform an LCA (Life Cycle Assessment ) methodology with a cradle to grave approach. The wood used for pelletization is from sawdust, wood shaving from hardwood and softwood.
The pelletized wood is then used for generation of heat. We compare the LCA of wood pellet with Natural gases LCA . We consider three scenarios for this LCA . Scenario 1: Heat production from wood pellets produced using conventional electricity (Thermal).Scenario 2: Heat production from wood pellets produced using wind energy.Scenario 3:Heat production from natural gases.
FUNCTIONAL UNITThe result are presented in terms of the functional unit to be the production of One MegaJoule (1 MJ) of heat when sources of energy are burnt, in order to compare the environmental impacts of three scenarios with a similar basis.ALLOCATION METHOD (Cut-Off vs APOS)Pellet production is a single-product system; that is, only one product (wood pellets) is produced at the end of the production process, however, the input materials (raw materials) could be diverse e.g. wood shavings, sawdust, wood chips and logs.Natural gas production is also a single-product system because only gas is produced at the end of the production process.This study relies on the data provided by Ecoinvent 3.
2 for heat production from natural gas and wood pellet due to lack of time to create own production process or collect data from existing plants. However, these data were based on physical, economic and cutoff allocation methods. (See Appendix)SYSTEM BOUNDARIESThis study is restricted to Germany and the system boundaries of the energy systems include all processes starting from the extraction of natural resource through the production phase and end use of the product. However, processes involving the provision of natural resources; for example, growing of timber in the case of wood pellet production and location of oil rigs in the case of natural gas production were not considered in this study.Wood Pellet Harvested timber are transported to the sawmills where they are processed into various wood products. Byproducts like wood shavings and sawdust can be further processed into wood pellet.
Sawdust is collected and dried to a required moisture content, grinded and pelletized. This process is followed by drying and screening into various market sizes which are thereafter stored or packaged and transported to consumers.Production:Transportation:Pellets combustion:Natural GasOil is extracted from oil fields and transported to a plant for oil and gas separation. The gas is further purified by removing condensates, water, hydrocarbon gases, nitrogen and methane. This is followed by fractionation which give a highly pure natural at a very high pressure. This high pressure gas is transported to a compressor station where the pressure is reduced and transported to natural gas companies who then provide consumers with natural gas via small low pressure pipes.IMPACT ASSESSMENT METHODWe are using the ReCiPe without long term effect impact assessment method for data analysis because it covers all impact categories required to answer our research questions which are climate change, human toxicity, depletion of abiotic resources, particulate matter and ozone depletion.
RESULTSAssessment results are presented and described with appropriate detail.Main findings are emphasized. Results are rounded appropriately.Graphs and tables are clear (legend, unit, colour choice, captions, …)Uncertainty is quantitatively assessed (sensitivity analysis, MC analysis)This section describes the results of the two energy systems based of the three different scenarios explained in method and data handling section above.Climate Change:REFERENCEThe European wood pellet markets: current status and prospects for 2020APPENDIXProcessesHeat Production from Natural GasThe data “heat production, natural gas, at boiler atm.
low-NOx condensing non-modulating <100kW | heat, central or small-scale, natural gas | cut-off, U" provided on Ecoinvent 3.2 was selected because of the following reasons:It represents an efficient production system for natural gas which involves low NOx emission.It considers a small-scale of heat productionThe boiler type considered in the heat production is a condensing non-modulating system of 10kW gas input.
It is suitable for our study area – Germany; considering that Germany imports natural gas from Russia and therefore a part of the market for natural gas; which is represented and/or included in this data. The dataset describes the transport needed for an average export of Russian natural gas and gas losses and emissions during seasonal storage.Heat Production from Wood PelletThe data “heat production, wood pellet, at furnace 9kW | heat, central or small-scale, other than natural gas | cut-off, U” on Ecoinvent 3.2 was considered for this study because:It considers a small-scale of production.It considers all raw materials possible for the production of wood pellet – sawdust, wood chips and shavings.The pellets produced with this process match the characteristics of the German standard of quality DIN-plus (certification).It considers boilers with nominal capacities in the approximate range of 5 to 20 kW.The process describes the combustion of wood pellets until heat production at the boiler outlet.The process included the infrastructure, the wood requirements (average pellets, moisture content = 10%), the emissions to air, the electricity needed for operation, and the disposal of the ashes.The two heat production systems are thus comparable on the following basis:They both consider a small production scale.They both are suitable for the study region – Germany.Both processes incorporate a boiler system within the range of 5 to 20kW.