House of Lords - Science and Technology

Select Committee on Science and Technology First Report

CHAPTER 3: POSSIBLE APPLICATIONS AND BENEFITS

3.1 The possible industrial uses of non-food crops depend on the oils, fibres, starches and other chemicals (e.g. proteins and pigments) that each crop contains. We have received details of a wide range of end products derived from plant materials. It is not the purpose of this report to chronicle them individually, and in this section we have grouped them together under the following headings: energy crops, industrial materials (oils, starches and fibres) and speciality chemicals.

3.2 In the energy sector, the main United Kingdom focus is on electricity generation from bulk quantities of combustible plant material, although oils and starches that can be processed into liquid fuels are also of interest (MAFF QQ 4, 15, British Sugar Q 421, Shell Q 214, ADAS Q 276). As industrial materials or speciality chemicals, products derived from plants have properties, such as biodegradability and low toxicity, which can represent improvements on equivalent products derived from petrochemicals (ACTIN Q 65, Leaver Q 295, Walker Q 352). Other plants provide materials for which synthetic equivalents would be very difficult to produce (ICI QQ 526 - 528).

Energy Crops

3.3 The three main ways that crops can be used as energy sources are; biomass for combustion or gasification, for heat, electricity or combined heat and power; biomass for fermentation into bioethanol fuel; and plant oils for diesel fuel. All these methods provide renewable sources of energy and reduce net emissions of CO₂ compared with the use of fossil fuels (MAFF Q 4, Powell Q 363).

BIOMASS FOR ELECTRICITY GENERATION

3.4 To stand a chance of economic viability, crops to be used as a source of energy for electricity generation need to be able to generate large volumes of high density, low moisture material from a small area of land in a short period of time. In the United Kingdom, the crops considered to be able to meet these requirements most effectively are willow and poplar short rotation coppice (SRC) (ACTIN Q 42, Biogen Q 202). Other crops being considered include the perennial grass, miscanthus (Biogen QQ 202, 209, BICAL p145). Waste straw and other by-products from arable crop production can also be used in this way (SCRI pp216, 218).

3.5 Willow SRC is a densely planted, rapidly growing crop that regenerates from the cut stumps, and can be harvested on a three year cycle. The current United Kingdom mean yield is around 7 tonnes of dry matter per hectare per year. However, plant breeding research has given rise to expectations of doubling that yield, with some test sites in Sweden producing as much as 22 tonnes of dry matter per hectare per year (Biogen Q 197). We visited Project ARBRE in North Yorkshire (visit report in Appendix 3), which will be the first power station in this country to be fuelled by SRC (augmented by forestry residue) and is aided under the United Kingdom Non-Fossil Fuels Obligation (NFFO). The electricity generating process at ARBRE will have four stages:

Drying the chipped willow stems using waste heat.

Gasification, where the chips thermally decompose to form a combustible gas, steam and solid carbon char. The main components of the combustible gas are CO, H₂, and CH₄.

Gas cleaning, where any tars and impurities are removed from the gas.

Electricity generation using a two-stage process: a 4.75 MW gas turbine and a 5.25 MW steam turbine.

3.6 Pollution from a SRC power station is expected to be low. The flue gases are likely to be cleaner than those from coal or oil-fired power stations, and the CO₂ released during combustion matches the amount absorbed during the SRC growth. The ash waste contains potash, which has value as a fertiliser. Other environmental advantages of SRC come from the ground cover which such crops provide: SRC is expected to provide a useful wildlife habitat and may support a diverse set of bird species (Kew p205, ADAS Q 289). It is also possible that SRC can be grown without intensive use of pesticides, again good for wildlife (MAFF Q 17, ARBRE p137). Fertilisers may be helpful to boost yields but, since the SRC is not destined for food use, it may be an acceptable crop to be fertilised with sewage sludge (NERC p200) thereby helping to dispose of an unwanted material.

3.7 Problems associated with SRC as a crop include its high water requirement, diseases (especially willow rust) and pests including beetles and rabbits (NERC p200, IACR p183 and Appendix 3). Rabbits are particularly troublesome when the crop is being established. Scaling up small field trials to widespread industrial production may worsen the problems from disease and some pests, but larger plantations will reduce the proportion of costs from protective fencing.

3.8 Like SRC, miscanthus provides a good habitat for wildlife. It is harvested annually with re-growth from its perennial rootstock (Biogen Q 297). Unlike willow and poplar, miscanthus is not a native United Kingdom species; it currently has few disease or pest problems (IACR p183).

3.9 Other costs associated with growing SRC or miscanthus are storage, in particular to prevent rotting between harvest and use (Bruce Q 155), and establishing the crop, especially with SRC where no significant harvest can be expected for the first four years (ETSU p160). A major consideration is the cost (financial and in terms of energy inputs) of transporting the fuel from the farms, and consequently SRC needs to be grown near to the power station (see Appendix 3). A project such as ARBRE will consume the output of up to 2,300 hectares of SRC (ARBRE p136), so good sites for biomass power stations will be those with plenty of available land nearby. Such sites are unlikely to be close to major population centres.

3.10 Existing projects, which are on only a very small scale, include SRC projects in Northern Ireland (MAFF Q 13), a 31 MW power station in Cambridgeshire that will use cereal straw for fuel, and a forest waste plant near Carlisle. Increasing the scale, and development of the technology and plant varieties, are expected to reduce the overall costs of generating electricity from biomass (MAFF QQ 10, 11, Biogen Q 179, Shell Q 233). We discuss relative costs below in Chapter 5. There are plans to develop more biomass power stations in the United Kingdom.

BIOETHANOL

3.11 Ethanol produced by fermentation of sugar can be used as a fuel in internal combustion engines. In certain countries (notably Brazil) where the climate is suitable for growing sugar cane, and large quantities of cheap sugar are available, bioethanol has been produced as a substitute for petrol (or to mix with petrol) to provide a renewable source of fuel for automotive transport, and as a source of hydrogen for fuel cells[8]. In the United Kingdom, sugar is produced from sugar beet, and is not currently available at a sufficiently low price to make bioethanol production viable[9]. However, we received evidence from British Sugar of a new bacterial process that can be used in place of the traditional yeast-based fermentation. The bacterial process makes use of a wider range of sugars and breaks down cellulose as well as smaller carbohydrates (QQ 421, 454). This means that the ethanol yield can be up to twice that obtained from the same biomass through fermentation with yeast.

3.12 The new process is currently being used in a plant in Louisiana USA, and British Sugar is interested in the possibility of its being applied in the United Kingdom. The bacterial process may make bioethanol a more competitive fuel here, or at least provide a way of adding value to waste agricultural products. British Sugar is also investigating the possibility of applying the bacterial process to fodder beet, in order to utilise plant capacity and the Company's expertise in handling this type of crop.

BIODIESEL PRODUCTION

3.13 The long-chain hydrocarbon structures of plant oils give them some similar characteristics to fossil diesel fuel. Methyl ester made from oilseed rape can be used in unmodified diesel engines (ETSU p159). Biodiesel has environmental advantages over traditional diesel fuel as a result of being renewable and biodegradable, and because it burns with low emissions of sulphur compounds and particulates (ABI p112, BABFO p139).

3.14 Questions about the overall competitiveness of biodiesel are raised by its low energy output-to-input ratio (2:1 - ETSU p159), the high cost of producing biodiesel (the British Association for Biofuels and Oils provided a figure of 2 or 3 times that of fossil diesel - p139) and the limited availability of rapeseed oil at a competitive price, which stems in part from the support of rape seed for food and animal feed uses. Even so, biodiesel is better developed in some other EU countries, notably France and Germany, than in the United Kingdom.

3.15 It is also technically possible to produce synthetic gasoline or diesel fuel from woody biomass. This involves gasification followed by further processing.

Industrial Materials

OILS

3.16 The oils found in plant seeds consist of fatty acid molecules whose chemical properties are dictated by the carbon chain length and the number and location of unsaturated bonds. The seeds of different species and varieties have their own range of fatty acids, making them suitable for particular applications or processing techniques. The main oilseed crops grown in the United Kingdom are linseed and oilseed rape; oils from these crops and other plant oils are also widely available on world markets. Linseed oil has many long-standing uses, including the manufacture of linoleum (hence the name of that material), putty and paint. During our inquiry, three main applications of plant oils were discussed: as lubricants, to make surfactants, and in paint formulation.

3.17 Certain plant oils can be used as lubricants without significant chemical processing. The Mobil Oil Company provided us with evaluations of rapeseed oil as a lubricant and hydraulic fluid (p196). Rapeseed oil has been examined as an alternative to mineral oil because it is biodegradable, renewable and has low toxicity. Mobil concluded that it is an excellent lubricant that can equal or surpass the performance of mineral oils in several applications. In one niche application - metal cutting - oilseed rape-based cutting oil provides a significant economic advantage to the end user. In some markets overseas, use of such products is mandatory; for example, we noted the use of low toxicity biodegradable chainsaw and engine lubricants in environmentally sensitive areas in Sweden and Austria (Walker Q 339).

3.18 The presence of an acidic chemical group and a long chain hydrocarbon in each fatty acid molecule means that plant oils can have important surface activating properties for mixtures of polar and non-polar materials (for example water and oil). Soaps and detergents for domestic use based on short-chain fatty acids (typically from palm or coconut oil) have been added to by a whole range of surfactants with uses in industrial cleaning and the agriculture, cosmetics and pharmaceutical industries (RSE p212). In principle, all classes of surfactants could be made from renewable plant materials; products from these sources tend to offer biodegradability and low toxicity (Gunstone p178).

3.19 The ability of unsaturated oils to oxidise and polymerise means that plant oils can be used as film-forming agents in paints. Reactive oils that polymerise on exposure to air or sunlight are known as drying oils. Many paints currently include volatile organic compounds (VOCs) to regulate their drying and film-forming properties; legislation limiting VOC use (see Box 6 below) has promoted interest in natural drying oils for new formulations of paint and printing ink (ACTIN Q 46). Linseed oil has been used as a drying oil in paint formulation (ICI Q 496), but other oil types (e.g. calendula oil - ADAS QQ 286, 287, p127, RSE p212) have been proposed as alternatives that have fewer drawbacks (especially less yellowing with age) than linseed. Further work in producing new varieties with optimised oil content and harvesting characteristics is required before new oils from garden plants like calendula (pot marigold) can be made available on a large scale.

3.20 The original varieties of linseed and oilseed rape were high in linoleic and oleic fatty acids respectively, but selective breeding programmes have been used to produce different varieties with oil contents tailored to different end uses. For example, Croda use a variety of oilseed rape that contains 50-60 per cent erucic acid to make erucamide, which has a market as a slip agent for polythene and in injection-moulded plastics. Erucamide is a large, relatively complex molecule and consequently attempts to produce it synthetically from petrochemicals would be very expensive (see Appendix 3).

STARCHES

3.21 Starch molecules are polysaccharides, made up of repeating glucose units. The physical and chemical properties of different types of starch depend on the way the polysaccharide chains branch. The industrial uses of different starches are determined by their ability to form granules or cross-links. Many UK markets for starch as an industrial non-food material are well established, but at present are almost entirely supplied by imported starches (mainly maize starch) (Royal Society p206) which have the characteristics which industry requires. The possibility of replacing imported starches with the main starch crops grown in the United Kingdom (wheat and potatoes) is being investigated (ADAS p131).

3.22 The main industrial uses for starch in the United Kingdom are in paper and cardboard manufacture, adhesives and surfactants. Areas of growing research interest include plastics and low-phosphate detergents (Royal Society p206, ADAS p131). ICI have recently been investigating the potential of starch to replace petrochemical monomers as film-forming agents in paint (ACTIN Q 46). The BBSRC highlighted (Q 128) low density packaging materials made from starch that would have the clear advantage of biodegradability over existing materials made from expanded polystyrene. ADAS provided evidence of the Oatec project, part of which involves the use of oat starch powder as a lining for latex surgical gloves (Q 237, p124). Other starches from crops such as Jerusalem artichoke and quinoa may have some specialist applications (ADAS p131), but the main opportunities in the United Kingdom appear to be for mainstream cereal starches.

FIBRES

3.23 Fibres are found in the stems and leaves of plants and sometimes in the seed casings (e.g. cotton fibres). The fibres can have particular characteristics (strength, lightness, softness, water absorbency) that make them useful for industrial purposes. Flax and hemp were the two main types of plant fibre discussed during our inquiry. Both these crops are grown on a limited scale in the United Kingdom under EU support programmes. Miscanthus, as a source of useful fibres, was also mentioned (BICAL p146, RSE p213).

3.24 The useful fibres of flax and hemp are found on the outside of the plant stems, and these need to be separated from the inner, woody material before use. The process of liberating the useful fibres (retting) relies on bacteria to break down partially the bonds between the fibres and the other stem material. The quality of the fibre is determined by the retting process, and we received evidence of interest in developing more controlled ways of retting flax and hemp for more predictable fibre quality (Robin Appel Q 93, Bruce Q 155). The relict stem material from hemp retting has found a market as animal bedding (Hemcore Q 80).

3.25 Woven textiles were identified as one of the major markets for plant fibres. Linen from flax has traditionally been a high value product, but more recently flax has begun to be blended with other fibres; a market for hemp clothing has also developed[10]. The fibres can also be used for making insulation materials and geotextile matting to reduce soil erosion on slopes (Robin Appel Q 81). Many kinds of plant fibres can be used to make fibreboard and particle board.

3.26 Paper making is another area where plant fibres have applications. The strength of hemp and flax fibre means that using even small amounts can reduce the proportion of virgin fibre required to make good quality recycled paper (SCRI p218).

3.27 Composite materials made from plant fibres mixed with resin are attracting great interest as replacements for glass fibres. The plant fibres offer a better strength-to-weight ratio than glass fibre (Robin Appel Q 81), do not cause skin irritation, and can biodegrade or be burnt to recover energy (Hemcore Q 80). Internal panels for cars (in particular, in the German automobile industry) look like an interesting market for these materials.

Speciality Chemicals

3.28 There are a large number of plant chemicals that could have some value or functionality in particular niche markets. We received evidence of a number of low volume, high value products that could be developed from plants for cosmetics, healthcare, and dyestuffs.

3.29 Specific fatty acids and essential oils are of value in cosmetics and "soft" healthcare (e.g. dietary supplements), as well as having possible uses as fine chemicals for research or small scale industrial processes. Lunaria (honesty) oil contains novonic acid which may have medical applications (see Appendix 3), borage and evening primrose both contain gamma linoleic acid, and the many uses of hemp oil in cosmetics were described in evidence from the Body Shop (Q 531).

3.30 We received evidence on woad as a source of indigo dye; a new water extraction process has been developed and a potential market in plant derived printing inks for bubblejet printers has been identified (ACTIN Q 60, Reading p228).

The "Roofless Factory"

3.31 The evidence we received regarding speciality chemicals extended beyond the extraction of useful materials from existing plant varieties. The possibility of applying biotechnology to produce improved varieties or even to generate entirely new chemicals in plants, especially for medical applications or for the polymer industry, was often raised (Leaver Q 295, BBSRC QQ 123, 139, DuPont, Q 381). Many advantages were pointed out to us. Using plant biochemistry to produce materials for bulk or speciality markets would provide renewable sources of industrial materials. In addition, such developments could make use of the United Kingdom's knowledge base to produce complex chemicals which are currently prohibitively difficult and expensive to synthesise.

3.32 Some processes involving bacteria have already been successfully developed to produce complex new chemicals. Genetically modified bacteria are currently used to produce pharmaceuticals, but since bacteria need warmth and nutrients to grow, the fermenters in which they are nurtured need high energy inputs and constant monitoring. The end products are therefore expensive. Costs could be reduced if the same materials could be produced routinely in plants, since the energy inputs would be provided by the sun, and the processes could be conducted on a larger scale. In 1998, the first human clinical trials of vaccines derived from genetically modified plants were reported in the scientific literature. In the United States, plant biotechnology companies have already acquired farms on which to develop pharmaceutical production facilities (BBSRC p144).

3.33 Genetic modification is a technology that has caused much controversy. Although its application in crops not destined for food use may not raise the same concerns as in crops for human consumption (MAFF Q 33), others persist. As the BBSRC pointed out to us, "the environmental and ecological implications are not yet known" (p143). Some witnesses gave evidence that they were trying to avoid the use of genetically modified materials (Body Shop QQ 553-555), arguing that it would be harmful to their image among their customers (Hemcore Q 94).

3.34 However, genetic modification is not the only means of developing new products (see Box 5). The opportunities are wide-ranging. Plants already make about 100,000 chemicals (Leaver Q 295), and it is becoming increasingly possible to develop plants containing materials designed for particular end uses by using a variety of different techniques. Several witnesses highlighted the potential for conventional plant breeding programmes to bring benefits to the non-food crop sector (MAFF QQ 8, 9, BBSRC Q 129, Hemcore Q 94, Biogen Q 197). This potential, however, needed to be exploited more effectively. The intensive work to improve the yield and other qualities of food crops was contrasted with the lack of development of non-food crops (UKELA p 221).

Box 5

Selective Breeding, Genetic Modification and Non-Food Crops
For centuries, agriculture has modified the genetic constitution of plants by selective breeding. In selective plant breeding, the genes of individual plants are mixed by conventional breeding, and the resulting offspring screened for those that show desired characteristics. The chosen offspring plants are then subject to further rounds of breeding and selection until the desired characteristic is exhibited reliably and to the required degree.

Advances in biotechnology are making it increasingly routine to link certain characteristics of an organism with particular genes (i.e. specific segments of DNA) which it possesses. It is also possible to isolate individual genes and copy or alter them. Once copied or altered, the genes do not have to be put back into the organism from which they came, but can be put into a different species altogether. The term "genetic modification" refers to these methods of altering the genetic make-up of an organism. Genetic modification can be used to change certain characteristics of a plant variety or to transfer characteristics (via copied genes) from one species to another.

So far as crops are concerned, genetic modification techniques have been used to give existing crops traits that make them easier to grow (such as herbicide tolerance and resistance to insects). Varieties of soya, maize and rapeseed that have been modified in this way are the result of studies of plant genetics that took place a decade ago. Many examples are already grown commercially in the USA, while in the EU trials are under way.

The next generation of genetically modified crops is set to move away from varieties developed simply for ease of farming to ones in which the mixture of chemicals which the plants produce (e.g. fatty acids, carbohydrates and proteins) is altered. Changing the profile of the plants' chemical constituents is of interest to the food sector (to give benefits in nutrition or cooking properties) but may also have value for non-food crops. Some genetically modified varieties of this type are already available (e.g. soybeans with a reduced saturated fatty acid content) and many others are expected to be developed over the next five years or so.

Further developments could result in crops producing specific chemicals for industry that plants currently do not make at all, using sunlight as a source of energy. Developing suitable plants may however require modification of a greater number of genes than has been necessary to produce the current genetically modified crops (e.g. those with herbicide resistance), and thus may be more difficult to achieve. Current expectations are that developing the knowledge and technology required for some of these products will take at least five to ten years of research. This concept is sometimes referred to as the "roofless factory".

Genetic modification raises issues of wide public concern with respect to the potential impact on the environment, even when not directly linked to the human food chain. The need for carefully-controlled experiment and rigorous evaluation of environmental issues is another factor which must inhibit the development and acceptability of such products. However, advances in biotechnology, such as molecular marker assisted selection, also offer methods of accelerating the selective breeding process without using genetic modification (BBSRC Q 139). If the gene that produces the desired characteristic has been identified, the offspring can be screened for this gene without waiting for the plants to grow and be tested. This technique may be especially valuable for plants that take many years to develop fully (IACR p73).