Greenhouse gas emissions of wood chips and wood pellets

Transcription

1 Greenhouse gas emissions of wood chips and wood pellets

2 Disclaimer: All reasonable measures have been taken to ensure the quality, reliability, and accuracy of the information in this report. This report is intended to provide information and general guidance only. If you are seeking advice on any matters relating to information on this report, you should contact the ERI with your specific query or seek advice from a qualified professional expert. 1

3 Preface Completed by Dr Neil James (Environmental Research Institute, North Highland College UHI, Scotland) for BioPAD, a project of the Northern Periphery Programme. The BioPAD project aims to improve our understanding of the links between supply and demand by looking at supply chains for a variety of bioenergy fuels and different ways of converting these fuels into sustainable energy. Understanding the supply chains and the ways bioenergy moves from fuel source to energy provision will help the establishment of robust and efficient supply services which can match local demand. BioPAD is led by the Western Development Commission (Ireland) and is funded under the ERDF Interreg IVB Northern Periphery Programme (NPP) It has partners in Scotland (Environmental Research Institute, UHI Northern Ireland (Action Renewables and Finland (Finnish Forest Research Institute, Metla 1

4 Emissions of wood chips and wood pellets 1. Introduction This report aims to provide a brief summary of the potential differences in greenhouse gas emissions arising from the use of wood chips and wood pellets for the Kilbeg village site of Sabhal Mòr Ostaig (SMO), UHI. It should be noted, however, that a report of this size and scope cannot take into account all sources of emissions, and therefore care should be taken when interpreting the findings. 2. Greenhouse gases Greenhouse gases (GHGs) are released into the atmosphere during the combustion of woody biomass including wood chips and wood pellets. Since wood is a renewable source of energy, its combustion can be considered to be carbon neutral, if sourced from sustainable sources. In other words, the GHGs released during combustion are considered to be equal to that absorbed during tree growth. In this study we assume this to be the case in all examples given. There are many other sources of GHG emissions release which occur along the wood energy supply chain, including those attributed, for example, to harvesting/drying of wood, wood pellet production, machinery etc. There are also factors which complicate the ability to estimate GHGs for each sector. For instance, wood pellet production can be energy intensive, but if factories are themselves powered by wood fuel, attributing emissions may not be appropriate. We do not, therefore, take into account the emissions associated with the production of wood chips or wood pellets in account in this study. 2

5 The most significant factor contributing to GHG emissions release is transportation of wood fuel. Therefore, in the absence of a full, extensive analysis of the emissions from wood chip and wood pellet supply for SMO, we concentrate on this aspect, and make a comparison of the likely GHG emissions resulting from the transport of either a. wood chips from Tormore forest, or b. wood pellets from Invergordon, to the Kilbeg village site of SMO. 3. Wood chips Several important assumptions have been made in calculating GHGs produced from the use of wood chips in the planned development at SMO. It is assumed that: Energy demand form biomass is kwh per year kg wood chips per year are required GHG emissions from transporting wood chips approximate those in the case study report by Bio-Renewables Ltd (2004) a Table 1. Greenhouse gas (GHG) emissions arising from the transport of wood chips from Tormore forest to SMO. Year Cumulative GHG emissions (kg CO 2 e) a 56.74kg CO2 e per year from the transport of 29.5 oven dry tonnes of wood slab during five trips a year, each of 10km using a tractor and 14 tonne trailer at an average speed of 30km per hour 3

6 GHG emissions arising from the transport of wood chips from Tormore forest to SMO would be approximately kg CO 2 e per year The cumulative total emissions using wood chips would exceed 1418 kg CO 2 e after 25 years. 4. Wood pellets The following assumptions have been made when calculating GHG emissions associated with the potential transport of wood pellets to SMO: Energy demand form biomass is kwh per year kg wood pellets required per year Journey distance: 102 miles (Invergordon to SMO) Diesel fuelled articulated lorry used for transport (>3.5t 33t), with an average payload of 5.51 tonnes kg CO 2 e per mile associated with articulated lorry b Articulated lorry is 50% laden on average during return journey (travel to SMO undertaken whilst 100% laden, return journey is 0% laden) 3 return journeys made per year b 4

7 Table 2. Greenhouse gas (GHG) emissions arising from the transport of wood pellets from Invergordon to SMO. Year Cumulative GHG emissions (kg CO 2 e) GHG emissions arising from the transport of wood pellets from Invergordon to SMO would be approximately kg CO 2 e per year. Over kg CO 2 e would be released over 25 years if wood pellets are delivered to SMO. 5

8 5. Wood chips vs wood pellets In this section we compare the emissions associated with the potential transport of wood chips from Tormore forest with those from the transport of wood pellets from Invergordon. Figure 1. Cumulative greenhouse gas emissions (GHG) in kg CO 2 e arising from the transport of wood chips from Tormore forest, or wood pellets from Invergordon, to SMO. Figure 2. Cumulative greenhouse gas emissions (GHG) savings in kg CO2e arising from the transport of wood chips from Tormore forest, rather than wood pellets from Invergordon, to SMO. 6

9 Table 3. Savings of greenhouse gas (GHG) emissions arising from the transport of wood chips from Tormore forest rather than wood pellets from Invergordon to SMO. Year Cumulative GHG emissions saved (kg CO 2 e) The supply of wood chips rather than wood pellets to SMO would save over 800 kg CO 2 e from transportation per year. After 25 years, the total emissions saved would exceed kg CO 2 e. Savings after 25 years are approximately equivalent to the yearly CO 2 e emissions of 4 UK households. c The GHG emissions associated with the delivery of wood chips to SMO are approximately 6.4% of that associated with the delivery of wood pellets from Invergordon. c Assuming each household is responsible, on average, for 5.1 tonnes of CO 2 e emissions (including those from gas, solid fuel, and electricity). 7

10 6. Government reporting figures There is a difference between the GHG emissions reported here for wood chips and wood pellets, and GHG emissions calculated according to emission factors used by the UK Government, which businesses are recommended to when voluntarily reporting scope 3 emissions. d In this report we have attempted to calculate GHG emissions with greater accuracy according to the situation pertaining to the new installation at SMO. However, for the purposes of clarity, we also provide GHG emissions according to the recommended values of the UK government. The figures we present include the extraction, refining, distribution, storage and retail of wood chips and pellets, using standardised, national averages. These are equivalent to WTT (well to tank) Scope 3 emissions. In this instance it is assumed, in line with UK Government requirements, that: GHG emissions from wood chips are kg CO 2 e per kwh GHG emissions from wood pellets are kg CO 2 e per kwh And that: Energy demand form biomass is kwh per year kg wood pellets required per year, or kg wood chips required per year d Scope 3 emissions, also referred to as other indirect. Are defined as Emissions that are a consequence of your actions, which occur at sources which you do not own or control and which are not classed as scope 2 emissions. Examples of scope 3 emissions are business travel by means not owned or controlled by your organisation, waste disposal which is not owned or controlled, or purchased materials or fuels. 8

11 Figure 3. Cumulative scope 3 greenhouse gas emissions (GHG) in kg CO2e arising from the transport of wood chips from Tormore forest, or wood pellets from Invergordon, to SMO. Figure 4. Cumulative scope 3 greenhouse gas emissions (GHG) savings in kg CO 2 e arising from the transport of wood chips from Tormore forest, rather than wood pellets from Invergordon, to SMO. 9

12 Table 4. WTT scope 3 greenhouse gas (GHG) emissions arising from the transport of wood chips from Tormore forest, or wood pellets from Invergordon to SMO. Cumulative GHG emissions (kg CO 2 e) Year Wood chips Wood pellets Emissions saved using chips rather than pellets The supply of wood chips rather than wood pellets to SMO would save over kg CO 2 e of scope 3 emissions per year. After 25 years, the total scope 3 emissions saved using wood chips rather than wood pellets would exceed kg CO 2 e. Scope 3 GHG savings after 25 years are approximately equivalent to the yearly CO 2 e emissions of 8.6 UK households c The scope 3 GHG emissions of wood chips are estimated to be approximately 40.5% of that from wood pellets. c Assuming each household is responsible, on average, for 5.1 tonnes of CO 2 e emissions (including those from gas, solid fuel, and electricity). 10

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