Biomass Waste EFW
Overview
Biomass is a feedstock for energy from waste processes. It is used in several different forms to produce energy and this effects the amount of power generated due to differences in variables like Moisture Content and Calorific Value. The different forms of biomass used in EfW processes are outlined below in the table[1].
| Waste | Overview | Tonnage (mt) '16-'17 | Power Generated (GWh) '16-'17 | |
|---|---|---|---|---|
| Wood Waste | Defined by the Wood Recycling Association Grading structure of A-C Wood tonnage fluctuates marginally throughout the year with the highest tonnages available during the summer months. The tonnage of wood is also heavily influenced by the level of activity in the construction sector although other sources are commercial packaging and wood delivered to household recycling sites. As of Qtr 1 2019 there are currently 23 waste wood facilities operating in the UK with another 3 taking a combination of waste wood and virgin wood and one a mixture of wood and MBM; 7 facilities are currently under construction. | 1.63 | 1273 | |
| Meat and Bone Meal (MBM) | MBM is the product of the rendering industry and under the Animal By-Products Regulations can only be disposed of via incineration with Category 2 disposed of by pressure rendering and then at an approved AD facility. Very little Cat. 2 material is processed separately from Cat. 1 so the main focus of the analysis is on Cat. 1. As of Qtr 1 2019 there are only two main facilities treating this waste stream with a third due on line at some point in the near future. Industry prediction is that this waste stream is expected to remain in balance. | 0.18 | 145 | |
| Agricultural | Includes straw and poultry litter (which is the by-product of the poultry industry and comprises excreta, spoiled feed, feathers and bedding material which is all readily combustible). There are four plants currently in operation treating in the region of 1.0Mtpa with the dominant markets for straw (animal bedding/feed) taking up around 80% of supply. Poultry Litter is sent to three large scale facilities with remaining tonnage sent to AD facilities and used in agriculture as a fertiliser. | 1.37 | 1225 | |
| Sewage Sludge | This waste stream is now managed exclusively in the UK as part of waste water integrated treatment process by the sewerage undertakers (two plants operated by Thames Water and the third by United Utilities). The trend in the sector is increasingly to use advanced AD to extract energy from the biogas generated. | 0.10 | 23 | |
| Process Residues | By-products from processing all forms of biomass that have significant energy potential and include kernels, shavings, sawdust, chaff) etc. As these residues are already collected at the point of processing they can be relatively inexpensive sources of biomass. | 0.09 | 45 | |
| Liquid Biomass | Also known as biofuel and is any kind of liquid produced from solid matter e.g. vegetable oils from sunflower, rapeseed or recycled vegetable oils, alcohol based fuels from fermented plant matter, corn etc. | NA | NA | |
| Virgin Wood & Energy Crops | There are currently 15 biomass facilities in operation taking virgin wood with another four taking a combination of waste wood and virgin wood; two remain under construction. Total MW capacity for the operational plants equates to 145 MWe. Energy crops ( Miscanthus, Short Rotation Coppice/Willow) represent less than 2% of the overall biomass market. | 2.36 | 1516 | |
| Total | 5.73 | 4226 |
Additionally, the details of the generating facility can affect the power output, for example the scale, technology used, or its ability to cogenerate heat and power[1].
EfW plants that operate using only biomass as a feedstock can be considered as producing renewable energy[2]. Biomass can be considered a renewable fuel because the growth of biomass removes carbon dioxide from the atmosphere and stores it in components of biomass such as soil, plants and trees, acting as temporary carbon storage[3]. Biomass is the largest source of renewable energy in the UK[3].
Biomass EfW
In 2017, there were 39 operational Biomass EfW facilities in the UK with an electrical output exceeding 2.5 MW; the total biomass capacity of these plants is 5.73 Mt (excluding fuel imported by Drax), and these plants combined produced 4,226 GWh of power. The biomass capacity of UK EfW plants is generally increasing. From 2016-2017 the amount of biomass being processed by UK facilities increased by 6.9%[1].
An example of a Biomass EfW facility in the UK is Welland Bio Power in Northamptonshire, accepting 72,000 tonnes of waste wood per year, and producing 10.6 MWe (gross) of low carbon electricity. Welland Bio Power utilises Nexterra Gasification technology and was developed by CoGen Limited[4].
Residual Waste EfW
Energy from Waste plants that use Waste Derived Fuel (WDF) but do not exclusively accept biomass will still have a portion of biomass in their feedstock. Often this is quantified as the amount of the C-14 isotope in the fuel compared to total carbon in the feedstock. This is an important parameter as the heat/electricity produced from an EfW plant that can be classified as renewable (and therefore eligible for subsidies e.g. ROC, RHI) is derived from the biogenic portion of the feedstock. Moreover, the amount of biogenic content relates to landfill cost saved by diverting this waste away from landfill[5]. This quantity of biomass in the feedstock also forms the basis of the Renewable Qualifying Multiplier (RQM) to calculate the quantity of payments made to a generator in line with the Contract for Difference (CfD) scheme[6].
The non-biomass portion of waste feedstock (e.g. plastics) produce a similar product gas to biomass-derived gas. Additionally, they both have similar fuel characteristics, like high volatile matter content and low fixed carbon content. Subsequently, this enables similar processing conditions and gas cleaning techniques to be used in waste and biomass EfW facilities. However, significant differences do still exist between these two feedstocks, for example, generally higher ash content and higher content of other contaminants in a mixed waste feedstock and these warrant specific changes in the EfW process[7].
Image above taken from Tolvik Biomass report[1].
References
- ↑ 1.0 1.1 1.2 1.3 Tolvik Consulting Ltd, 2017. UK Dedicated Biomass Statistics - 2017. [online] [Accessed 13 Nov. 2019].
- ↑ Defra, 2014. Energy from waste A guide to the debate February 2014 (revised edition). London.
- ↑ 3.0 3.1 Office for National Statistics, 2019. A burning issue: biomass is the biggest source of renewable energy consumed in the UK - Office for National Statistics. [online] Office for National Statistics. [Accessed 14 Nov. 2019].
- ↑ CoGen, 2019. Projects — CoGen. [online CoGen.] [Accessed 14 Nov. 2019].
- ↑ WRAP, 2019. A Classification Scheme to Define the Quantity of Waste Derived Fuels. Wrap.org.uk. [online] [Accessed 1 Nov. 2019]
- ↑ LCCC, 2019. Contracts for Difference Generator Guide. Low Carbon Contracts Company. London.
- ↑ Waldheim, 2018. Gasification of waste for energy carriers. A review. IEA Bioenergy, [online] ISBN 978-1-910154-56-4. p.16. [Accessed 14 Nov. 2019].