Safe and sound: Decentralisation with Miscanthus giganteus
The biggest advantage of growing Miscanthus giganteus and its various industrial applications, is that it lends itself to small-scale, decentralised production units, particularly suited for the rural area.
The rural – urban divide
56% of Europeans live in the rural areas. ‘They occupy over 90% of Europe’s territory and contribute 43% of Europe’s gross value' (1). Rural enterprises currently account for 55% of employment. The rural communities are growing diverse and ‘ increasingly mirror the spread of commerce and services seen in urban communities.' However, the governments tend to focus only on agriculture. The other problems that rural communities face nor the potential they offer in generation of more jobs or tackling environmental problems have not been completely realised (2).
One of the main concerns that has been neglected so far, are their energy needs. ‘Rural communities have different energy needs, and have a reduced and more costly choice than their urban equivalents. (Therefore) rural individuals have a larger carbon footprint than urbanites and need greater access to cleaner energy choices.' So far, these choices have been polluting coal, gas and wood (2).
Conventional power generation
Conventional power generation methods are wasteful. During the production of electricity, heat produced as a by-product had been treated as waste and channelled away through cooling towers back into the environment, unused (3). Consequently gas power stations have an efficiency of only 49-52%, while coal is the least efficient with 38% efficiency. This means of 100 tonnes of coal used, 38 tonnes give power, and the rest is wasted! (3,4). It is estimated that the heat lost currently in UK plants is enough to heat its homes (3).
Fig 1 (a): The difference between biomass CHP and a fossil fuel plant (earthmill.co.uk).
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Fig 1 (b): ‘CHP is far more efficient (wastes much less energy) than conventional power plants' (4).
CHP
The combined heat and power system (CHP), uses this wasted heat, greatly increasing the efficiency of the fuel used (See Fig 1). This happens by meeting heat requirements, ‘that would otherwise require additional fuel to be burnt' (5). This process is also called cogeneration. Using CHP, 70-80% of the fuel is converted to heat and electricity, that can be used for central heating and providing hot tap water. The proportion of heat to electricity varies with the system used. Some CHP have a reported efficiency of even 90%. CHP can work with all sources of energy – natural gas, biomass, biogas and liquid biofuels (6).
Though CHP are being promoted and becoming popular in the last ten years, it is not a new invention. ‘The world's first proper power plant (built at Pearl Street in New York City by Thomas Edison in 1882) was essentially a CHP design: it supplied both heat and power to nearby buildings in Manhattan' (4). When centralised large plants using fossil fuels began supplying electricity, the dual use was lost, as these plants were far from their end users (4).
Fig 2: The different fuels used in CHP (7)
Decentralised and Local
An essential feature of CHP is that it can be decentralised and local. Consumers can produce their own power and meet their heating needs simultaneously with CHPs. This has the additional benefit of saving the 7% energy that is lost during traditional transmission of electricity over long distances (3). However, the initial investment in equipment for a CHP system is high. The savings from reduced energy costs can offset the extra cost. Smaller units tend to be more expensive than larger ones, especially for this reason (8).
As of 2015, there were 2000 sites using CHP in UK. Large buildings like hospitals, care-homes, businesses and public sectors concerns have successfully used CHPs, bringing down their energy bills. For example Rotherham Hospital saved 273,000 £ in energy costs and 130,000 tonnes of CO2 in a year. Again in London, 40 fire brigade stations use CHP. Care-homes have saved approximately 15,000 £ per year too (3).
CHP for homes
Micro CHP for use in residential homes are also available, that can be powered by biomass and biofuels. They are popular in UK and Germany, but are less common in other parts of Europe. In warmer regions the ‘trigeneration system' that produces heating, electricity and cooling is more appropriate. The current models of CHP are improved and operationally simple enough ‘to plug and play' (6). Any surplus electricity that is produced can be sold to the local power grid. Since surplus power generation takes place during the day when power prices are highest, the producer benefits from these high prices (9).
The fact that Miscanthus powered CHP systems are not polluting makes it ideal, healthy and safe for domestic use.
CHP for Greenhouses
CHP in general is very useful for rural areas. The biggest advantage is that transportation costs of fuels, especially low density and bulky biomass fuels are reduced, since biomass, bioenergy crops and crop residues can be sourced locally. As in the urban areas, it can be used in homes and businesses. It is particularly useful in greenhouses. The heat, warms the green houses and the electricity provides lighting; in addition, the CO2 released in the exhaust gas from burning the fuel can be ‘scrubbed and used to promote plant growth'. The exhaust gas is cooled to 550C and supplied to the greenhouse (9).
Greenhouses whose temperatures and light are kept at a constant along with high concentrations of CO2 ensure better plant growth and more yield. Usually air has 350 ppm of CO2, but plants can use up to 700 ppm. Moreover, ‘CO2 fertilisation is suitable for nearly all plant types' (9).
Advantages of using Miscanthus in CHP
Every CHP system reduces carbon emissions, even those that use fossil fuel, as the amount of fuel needed is reduced. Consequently this reduces air and water pollution, as well as acid rain. With the emphasis on climate protection increasing, so is use of renewables as carbon neutral fuel. It brings us closer to meeting the 2050 zero carbon emission targets the world has set itself to combat climate change. EU has intermediate targets to increase the share of power from renewables to 20% by 2020.
The use of renewables (biomass, biofuels and biogas) as fuel has nearly doubled from less than 10% in 2005 to 18% in 2013 (See fig 3, 7). Evaluating the use of bioenergy crops, it was found that Miscanthus achieved the best GHG reductions, as it can be grown on marginal land, and needs little to no nitrogenous fertilizers, compared to crop residues from wheat and corn, or from short coppice crops like willow and poplar (10).
Fig 3: Renewables use in CHP fuel mix is increasing (7).
Miscanthus can be used in direct combustion, which is the oldest and simplest method, but has an efficiency of only 22%. In comparison, using Miscanthus in a CHP system increased fuel efficiency to 85 – 90%, especially in greenhouse use. Moreover, the low sulphur content in lignocellulosic fuels means it is less polluting than coal (think acid rain). Burning biomass produces mostly CO2 and only 2% of other GHG gases like methane and nitrous oxide that are 21 and 300 times more damaging to the climate than an equal weight of CO2 (11). Furthermore, the ash produced from using Miscanthus in a biomass boiler in a CHP, can be used as fertilizer (8).
The renewables are used more in CHP systems than in any other power generators as shown in Fig 4.
Fig 4: More renewables are used mostly in CHP (7).
Miscanthus in other energy systems
Miscanthus can be used to substitute coal in co-firing systems and in large units achieves an fuel efficiency of 35-45%. A co-firing plant in Drax uses up to 12% biomass, including Miscanthus grown in surrounding areas (12). Romania for example is reducing its carbon emissions, by using Miscanthus grown on large tracts of unused land, in large co-firing plants (13).
Gasification is another large scale method of power generation, that uses Miscanthus. ‘Currently, the biomass integrated gasification combined cycle is the most common approach for power generation from lignocellulosic biomass' (11). The carbon emissions are the least from this method. Both gasification and co-firing occur on large scales, but are still useful in reducing dependence on imports of biomass, when Miscanthus grown on marginal land or on contaminated land is used, to avoid carbon emissions from direct or indirect land-use changes.
Electricity generation through CHP in Europe
‘The EU currently generates 11.7% of its electricity using cogeneration' (7). Different countries have varying contribution, from a Slovakian high production (78.6%) to nil from Malta. Cogeneration is often used for local district level heating systems (7).
CHP, can generate jobs, especially in the rural sector when bioenergy crops are used as fuel. So can co-firing and gasification, since these plants are usually based outside urban areas, near their fuel source. Bioenergy crops based CHP and gasification pose no health risks through pollution during power generation, decrease transportation distance for fuels and provide cleaner energy to rural communities.
Miscanthus in a bio-based economy
Though Miscanthus giganteus is most popular as a bioenergy crop, it has many other uses. It can in fact drive a bio-based economy in rural areas (14). Since Miscanthus can be grown easily in temperate Europe, industries can be based in rural areas, so that the raw materials can be sourced from surrounding areas to avoid costs from long distance transportation as well as employ local people. These small scale industries can be spread over the length and breadth of UK or even Europe. This would invigorate rural communities and economy, which are both currently suffering from large scale migration of people to urban areas.
As the Guardian observed in 2015, ‘A lack of employment opportunities and affordable housing drives young people to the cities. This leads to the closure of schools, an ageing and increasingly dependent population, as well as a deterioration of health, transport and other services' (15).
The small-scale rural industries or businesses that Miscanthus can support are fibre-based. Its fibres are short, similar to cereal straw or hemp, influencing its uses (16).
- Biocomposites
One of the major applications of Miscanthus is in the production of biocomposites. Whole green biocomposites made from polymers (which are also biological in many cases) and a bio-filler like Miscanthus, have a wide range of applications, the most important of which are listed below.
a) Given its short length, Miscanthus has been found to be particularly useful in maufacturing medium density fibreboards, for use in construction and furniture.
b) Miscanthus can be used in making ‘Light natural sandwich materials' (LNS), with applications as ‘planes and mould structural parts with high form stability at low weight' (17). These LNS can replace plastic, metal and wood components in automotive and building interiors, lowering environmental impact (17,18).
c) Production of Bioconcrete, using locally available Miscanthus is being tested in Netherlands, to print 3-D houses (14, 9).
- Bioplastics
‘Currently, bioplastics represent about one per cent of the about 300 million tonnes of plastic produced annually', according to an European Bioplastic report based on 2015 data. The industry is seeing up to 100% increase annually worldwide, with most of the growth happening in Asia. The main obstacle for its development in Europe has been lack of support from national policy and schemes. Miscanthus has great potential as one of the possible raw material for bioplastics; biodegradable packaging is one of the common applications. As Fig 5. shows, crops for bioplastics need not compete for land for food (20).
Fig 5: Land use for all material production is only 2% (20)
- Paper and cardboard
Miscanthus fibre pulp has been used to make paper and cardboards. 50-70% of Miscanthus pulp is mixed with recycled waste paper to reinforce and improve the ‘mechanical characteristics of paper' (21). Making paper from non-wood sources has so far been more common in developing countries. Only 1% of the paper produced currently in Europe is from non-woody materials (17). Most of the non-wood raw material to make paper is imported. So, using locally grown Miscanthus can reduce imports and dependence on high carbon stocks like forests. Paper making requires low investment, is environment friendly and can produce a wide range of consumer products (22).
- Miscanthus as substrate in farming
Miscanthus fibres can be used to grow oyster and shiitake mushrooms instead of cereal straw and beech sawdust (c). It can also be used as bedding for animals, like dairy cows, horses, poultry etc (14, 23).
- Geotextiles
There is a growing interest to use the annual yielding Miscanthus to fabricate high value products like geotextiles. Geotextiles is a rapidly growing industry, given that it can be used in reinforcement, filtration, drainage, separation and protection. The majority of geotextiles are made from polyesters and polyproplene, and can be woven, non-woven or knitted. They are used to substitute sand, stone and gravel in places like roads, highways, drains, breakwaters, land reclamation and construction (24, 25, 26).
Conclusion
The national governments and EU need to urgently formulate policies and schemes that can provide the necessary incentive and means to revive rural areas, by promoting bio-based rural industries. Notably, since the expertise, technology, and markets to realise bio-based industries already exist. Some entrepreneurships like AgriKinetics have been taking the initiative, and spreading information of the innovations, since we believe a bio-based economy with proper environmental checks can be a win-win situation for all.
Sources
- Xinhua SX, Kommalapati RR and Z Huque. 2015. The Comparative Life Cycle Assessment of Power Generation from Lignocellulosic Biomass. Sustainability: 7: 12974-12987. doi:10.3390/su71012974
- http://www.kcpk.nl/algemeen/bijeenkomsten/presentaties/floris-van-tilburg (Retrived on 21.4.2106)
- Cappelletto P, Mongardini F, Barberi B, Sannibale M, Brizzi M and V. Pignatelli. 2000. Papermaking pulps from the fibrous fraction of Miscanthus x Giganteus. Industrial Crops and Products. 11: 205 – 21.
- Van Weyenberg S, Ulens T, De Reu K, Zwertvaegher I, Demeyer P and L. Pluym. 2015. Feasibility of Miscanthus as alternative bedding for dairy cows.Veterinarni Medicina. 60: 121–132.