For the most promising energetic utilisation pathway in greenGain the processing to wood chips and a further combustion via a Combined Heat and Power plant (CHP) was chosen and further assessed.
The biomass from DE-LCMW 1 hedge- and tree rows on banks (refer to the table 1: Potential and properties of landscape conservation and maintenance work (LCMW) biomass in the greenGain model regions; greenGain deliverable D4.2) mostly consists of woody biomass from trees and shrubs and can be used as logs and chips. Usually, it is not compatible with pelletizing or fermentation process. As firewood it is an appropriate fuel for fireplaces in the domestic sector. For the most promising energetic utilisation pathway in greenGain the processing to wood chips and a further combustion via a Combined Heat and Power plant (CHP) was chosen and further assessed. Figure 1 shows the process steps from the wood chips to the heating system. The wood chips are transported with a tractor with trailer or a truck to an intermediate storage where they are dried under a shed. To remove the small particle fraction and achieve a certain size range the wood chips are sieved and then transported to small heating systems. Medium-central heating systems are able to process wood chips in a heterogeneous quality therefore sieving is left out. Small heating systems are often applied in large households and farms. CHPs often supply central heating systems of public buildings and district heating networks.
Combined heat and power (CHP) is a highly efficient process that captures and utilises the heat that is a by-product of the electricity generation process. By generating heat and power simultaneously, CHP can reduce carbon emissions by up to 30 % compared to the separate means of conventional generation via a boiler and power station (Government UK, 2016).
It is mostly waste or used wood that is burned in the energy supply companies’ installations, which in many cases are set up to have electrical capacity levels between 10 and 20 MW. Conversely, in cities’ and municipalities’ installations are set up for a capacity of < 5 MWel in most cases. Mainly assortments of forest waste wood and also wood from landscape conservation areas in the region, as well as wood material from municipal properties is used. Via local and district heating networks, the biomass installations’ heat is made available to manufacturing, trade and service companies, as well as to housing cooperatives, private households and public buildings (FNR, 2016).
The role of fuel quality
For the combustion system and for the plant economy the quality of the fuel plays an important role. The key parameters that need to be taken into account for the fuel quality are the moisture content, the dimension of the chips, fines and dust content, origin of the chips and the ash content. The wood chips from hedge and tree rows have a moisture content of 30 – 45 % and usually a high proportion of bark and needles or leaves.
DE-LCMW 1 Hedge and tree rows on banks in FRI as feedstock for a LiPRO gasifier
To be suitable as fuel for the LiPRO CHP 50 KW the woodchips from DE-LCMW 1 Hedge- and tree rows on banks would need to be sieved to G30-G50 and dried to a water content of 15 %. This drying process requires an additional transport, handling and processing step. Drying is typically performed at biogas plants which have excess heat and the technical equipment for drying services. These pre-treated woodchips would be suitable to fuel for example a LiPRO gasifier and yield 50 KW power and 110 kW heat (LiPRO, 2016). Technical data of the gasifier are provided in table 1.
The average harvest of 15,590 LCM wood chips from the hedge and tree rows in Friesland per year would be sufficient to supply the yearly fuel consumption of nine LiPRO CHP 50 KW gasifiers with a yearly fuel consumption of 400 t wood chips (W15). This would replace around 1,559,000 litre of heating oil and avoid the respective CO2 emissions.
The LiPRO CHP is most suitable for heat and electricity consumers who need large amounts of heat and have access to inexpensive fuels from own and nearby land. Income can be generated by supplying electricity into the network and receive the compensation from the respective subsidy programme (EEG). Agricultural and forestry enterprises, industrial and commercial enterprises with high heat and power demand, hotel and restaurant enterprises, district heating grid operators to supply several buildings (residential, public buildings, sport and pool facilities) are especially suited for installation and operation. Figure 2 shows hypothetical locations and applications of the LiPRO plants if they would be installed in Friesland.
The yearly harvest of 15,590 LCM wood chips from hedge and tree rows on banks has a caloric value of 15,590,000 kWh which if burnt to heat would emit 155,900 kg CO2. The same heat amount 15,590,000 kWh achieved when burning fossil fuel oil to heat emits 5,129,110 kg CO2. Compared to heating with fossil fuel oil, a CO2 saving of 4,973 t CO2 can be achieved when heating with wood chips from LCMW (Carmen-ev, 2016).
According to the GEMIS model the Global Emissions Model for integrated Systems by the International Institute for Sustainability Analysis and Strategy the emissions factor are (IINAS, 2016):
0.010 kg CO2-emissions factor per kWh heat from Biomass (wood, pellets, Wood chips)
0.329 kg CO2-emissions factor per kWh heat from fuel oil (fossil)
0.250 kg CO2-emissions factor per kWh heat from natural gas
The figures and observations suggest that LCMW biomass in the region cannot constitute by itself a main biomass source for dedicated energy plants.
It can, however, be integrated in existing biomass supply chains. Local actors like forestry companies and other specialised service providers are key stakeholders needed to facilitate the harvest and use of LCMW biomass.
LCMW biomass as stand alone feedstock is feasible on a small scale like the example of the LiPRO CHP 50 KW. An installed LiPRO plant is operating on an organic farm in Grummersort, Germany. Half of the annual feedstock amount comes from the farm’s own hedges and the other half from nearby forest residues with a radius of 5 km radius. In 2015, during 7000 CHP operating hours, 210,000 kWhel were generated. About 90,000 kWhel were used at the farm and the rest was sold to the grid. The 420,000 kWhth were used at the farm for heating, hay drying and greenhouse operation. The plant is very positively perceived in the public. It is not that visible as wind turbines, feedstock supply does not compete to the food production and it uses local resources, which have to be handled anyway and through this way they can be valorised.