Select Committee on Innovation, Universities, Science and Skills Written Evidence

Memorandum 45

Submission from Plymouth Marine Laboratory




  Photosynthetic microbes, encompassing both microalgae and photosynthetic bacteria, are the most efficient users of the sun's energy and present enormous opportunities to produce bioenergy. As unique chemical factories they yield up to 40 times more biomass per unit area compared to land plants. Photosynthetic microbes have the potential to produce biofuel (biodiesel and biogas) and to reduce energy consumption and greenhouse gas (GHG) emissions in the sewage, solid waste, power and manufacturing industries.

  Close to market applications recommended for development include, the production of biogas and reduction in energy consumption associated with Primary Industries. Under intense International investigation is the capture of waste CO2 emissions and production of biodiesel. Central to the deployment of these applications is the large scale cultivation of the microbes using photobioreactor[152] (PBR) and photosynthetic biofilm (PSB) technologies. The UK has a strong research base in aquatic microbial bioscience and biotechnology although it now lags behind US and European effort to develop bioenergy technologies. We recommend research aimed at harnessing the capabilities of this untapped resource. Here we welcome the opportunity to provide evidence on the following applications:

Photosynthetic bacteria

    —  High quality pipeline biogas: photosynthetic bacteria can be used to purify low quality biogas from Primary Industries (eg sewage treatment, landfill, feed lots, food waste and municipal solid organic waste) to produce pipeline quality gas for network distribution.

    —  Biohydrogen: Ligno-cellulose can be used as a feedstock for photosynthetic bacteria to produce biohydrogen.


    —  Biogas. Microalgae grown using waste CO2 emissions can be subsequently anaerobically digested to produce biogas.

    —  Biodiesel: Molecular and genetic engineering of microalgal species high in lipids, grown using waste CO2 emissions have potential as an economically viable route to biodiesel.

    —  Biogas: Microalgae can reduce energy consumption in secondary and tertiary sewage treatment and resultant biomass can be converted to biogas.


    —  Biochemical, genetic, metabolic and ecological research aimed at harnessing the capabilities of photosynthetic and other microbial systems.

    —  Investment in development of platform PBR and PSB technologies including establishment of pilot and demonstration facilities.

    —  Facilitate International collaboration in areas with ideal climatic conditions (eg Ghana).


  Photosynthetic microbes (microalgae and photosynthetic bacteria) have the potential to produce biofuel (biodiesel and biogas) and reduce energy consumption and greenhouse gas (GHG) emissions in the sewage, solid waste, power and manufacturing industries. Here we provide background evidence on using photosynthetic microbes for bioenergy.

Figure 1


  As summarised in Figure 1 (refer to respectively labelled paragraphs), photosynthetic microbial consortia can be used to produce:

    A.  High quality pipeline biogas Conventionally derived biogas from bacterial anaerobic digestion is of low calorific value. Photosynthetic microbes can be used to convert this poor quality biogas to pipeline quality biogas by removing CO2 and H2S and replacing with hydrogen (Table 1). The total biogas potential for the UK equates to 6m T/y of oil equivalent and conversion of raw biogas to pipeline quality gas could double this energy value to around 12m T/y oil equivalent.[153] By combining cultured strains and natural isolates, robust anaerobic photosynthetic bacteria consortia capable of cleaning and upgrading biogas from a wide range of sources including landfill, sewage sludge digestion, abattoir and farm waste digestion, and municipal solid waste digestion can be achieved.

Sewage Biogas
Landfill Biogas
Natural Gas
Enhanced Biogas (estimated)

Energy content (MJ/M3)
Carbon dioxide
Carbon monoxide
Hydrogen sulfide
Chlorine (total CI)
22 mg/ m3

  Table 1: Calorific values and compositions of biogas compared to natural gas.[154]

    B.  Biogas production and reduction in energy consumption in sewage treatment. The energy required to treat sewage is high and the water industry is the fourth most energy intensive sector in the UK. Further tightening of water quality standards suggests energy costs will increase.[155] Over 10 billion litres of sewage are produced every day in England and Wales and it takes approximately 6.34 gigawatt hours of energy to treat this volume of sewage, almost 1% of the average daily electricity consumption of England and Wales. In total, the water industry used 7,700 GWh of energy in its operations during 2005-06, and emitted over four million tonnes of greenhouse gases, 1% of total UK greenhouse gas emissions.[156] We estimate that 50-70% of the existing UK sewage treatment plants could be retrofitted with photosynthetic biofilm (PSB) technology, where the main constraint on the remaining sites would be availability of suitable land area for installation. Photosynthetically derived oxygen from microalgal consortia could replace energy intensive activated sludge processes (Figure 2). Resultant biomass can be anaerobically digested producing raw biogas which can then be upgraded as above.

  Figure 2: Basic biological processes in wastewater treatment, illustrating the benefits of algal/bacteria consortia

    C.  Biogas production from microalgae grown on waste CO2 emissions. GHG emissions from power stations can be reduced by fixing CO2 using an autoflocculating microalgal consortia grown in photobioreactors (Figure 3). Resultant biomass can be anaerobically digested where the biogas is upgraded by a photosynthetic bacterial community to produce methane and hydrogen biofuel. Practical applications of microalgae biofixation of CO2 and biofuel production in wastewater treatment could lead the way to future applications, such as in the coproduction of biofertisers, higher value co-products (i.e biopolymers and animal feed) and possibly in the future to stand alone, dedicated, biofuel production systems endowed with a much larger global potential.

  Figure 3: Power station emission conversion into biofuel diagram

    D.  Biodiesel from microalgae. Molecular and genetic engineering of selected microalgal species for high lipid content needs research to provide economically viable biodiesel. Microalgae biosynthesise a wide range of commercially interesting bioenergy byproducts such as fats, oils, sugars and functional bioactive compounds. Many species are rich in lipids and hydrocarbons suitable for direct use as high-energy liquid biofuels, at levels exceeding those present in terrestrial plants, and also have potential as substitutes for the refinery products of fossil fuels. Hardly surprising considering that the majority of petroleum is believed to originate from microalgae. One species, Botryococcus braunii, in particular, has been widely studied.[157] The yield of oil from microalgae is predicted to be up to 100 times greater then land based crops at 7,500-24,000 litres of oil per acre per year compared to rapeseed and palmoil at 738 and 3,690 litres of oil per acre per year respectively. There is now renewed widespread International effort on developing microalgal based biodiesel although the UK is not currently part of this effort. The National Renewable Energy Laboratory (NREL) funded by the U.S. Department of Energy's Office of Fuels Development has recently reinstated research in this area.[158]

    E.  Biohydrogen from lignocellulose feedstocks. Because lignin is perhaps the second most abundant carbon polymer on Earth and thus a renewable resource, it is a candidate substrate for biofuel production, the most desirable of which is hydrogen. Of the enzymes responsible for hydrogen production, hydrogenase requires no ATP for activity but are reversible, thereby limiting hydrogen accumulation. Nitrogenase, the enzyme responsible for reduction of dinitrogen gas, also produces hydrogen but is very energy intensive. However, the nitrogenase reaction is essentially irreversible allowing pressurization of the hydrogen produced (Figure 4).. The advantage in photosynthetic bacteria is that they can obtain the energy necessary for hydrogen production through photosynthesis driven by the "free" supply of sunlight.

  Figure 4: The metabolic pathway leading to biohydrogen production in photosynthetic bacteria.


  The technologies described in this document are capable of being retrofitted to existing infrastructure. We outline here our predicted timescales and feasibility.

Table 2: (PML predictions)

Bioenergy Route
Carbon footprint

Biogas Upgrade
Low energy sewage treatment
Power station flue gas to biogas
Power station flue gas to biodiesel
Biogydrogen from ligno cellulose


5.1  Basic research

  There is clear strategic vision on bioenergy in Europe and the United States, with considerable resource investments at the bioscience end of the R&D spectrum. During the 1990s the UK was at the forefront of bioenergy development from photosynthetic microbes, but now UK R&D activities lag behind international leaders in this field. The UK has a strong research base in microbial bioscience and biotechnology and this should be utilised to provide maximum benefit within the international bioenergy market sector.

  Photosynthetic microbes can and will make a significant contribution towards satisfying the global need for clean, alternative energy sources. There is an urgent need for research aimed at harnessing the capabilities of photosynthetic and other microbial systems. The US Department of Energy has issued a call for Bioenergy Centers to develop microbial-based strategies that generate alternative energy sources from biomass, sunlight and other renewable resources. In addition, the European Science Foundation is considering a major funding initiative to support bio-inspired solar energy strategies. These programmes and private sector initiatives represent an exciting beginning to a long-term concerted effort to develop clean microbial solutions to the world's energy challenge.

  The continued development and improvement of these microbial "biorefineries" will require significant additional biochemical, genetic, metabolic and ecological insights into the relevant microorganisms. It is essential to acquire a systems-level understanding of energy capture and its transformation in order to direct the reaction products into pathways that produce alternative fuels or sequester greenhouse gases with increased efficiency. Additional research is required to ascertain whether communities of photosynthetic and non-photosynthetic bacteria could be tapped to provide clean energy or replace fossil-fuel-derived feedstocks. It will also be necessary to find economically viable biorefinery options, optimize the processes involved, and scale-up the systems. For algal biodiesel to become a more competitive option, metabolic and genetic engineering and strain selection for lipid production is required. Stable consortia, are essential to success and we recommend a multidisciplinary and systems biology approach is needed to develop, characterise and optimise microbial consortia.

5.2  Platform technology

  PBRs and PSBs as a platform technologies have wide reaching potential in bioenergy, CO2 mitigation and in high value bioactives. Future developments in molecular and cellular engineering of photosynthetic organisms will be implemented in PBR and PSB platform technology. Therefore it is important to invest in the PBR and PSB engineering and necessary IP to guarantee the UK's dominance in the international biofuel market. In addition to providing funding on fundamental R&D, Government should also fund pilot and demonstration plants.

5.3  National gas network

  The feasibility of using purified biogas in national gas grid network needs to be fully assessed. For example; how will the presence of low levels hydrogen in enhanced biogas affect the network and final combustion devices?

5.4  International Cooperation

  Ghana possesses the one of the best climates on Earth for biofuel production from photosynthetic microbes, where warm night time temperatures and high insolation will reduce the need for PBR insulation and therefore capital costs. By combining the expertise of UK algae biotechnologists and Ghanaian engineers, Ghana could become a net exporter of Biofuels to the rest of the World and provide a demonstration platform for Greenhouse Gas reducing technologies. A joint project, whilst producing a sustainable replacement for fossil fuels, will also benefit local sanitation, water supply and ultimately poverty through job creation.

  Several US and European groups are already planning PBR installations in Ghana for biofuel production, so the UK Government should build upon the existing close relationship with The Honourable President John Kufuor's regime and the Ghanaian people, to ensure that superior UK PBR and PSB technology can be implemented accordingly.


6.1  Solar Energy

  Photosynthetic microorganisms can capture solar energy, a free, abundant and under-used energy source. The amount of solar energy that strikes the Earth every hour (4.3 1020 Joules) is approximately equal to the total amount of energy that is consumed on the planet every year (4.1 1020 Joules). Therefore, capturing even a small fraction of the available solar energy could make a significant contribution to global energy needs. Photosynthesis plays a central role in all bioenergy production. It drives the first step in the conversion of sunlight into chemical energy and is therefore ultimately responsible for the production of feedstocks required for all biofuel synthesis.

  Land-based bioenergy crops create serious economic and environmental concerns, which include the sequestering of huge areas of arable land or ecologically sensitive regions (such as rain forests) for their growth, the introduction of competition to food production, and a concomitant increase in the price of staple food. In contrast, aquatic-based large-scale photosynthetic microbes culturing facilities can be sited on any land, including waste or industrial sites. Photosynthetic microbes use sunlight far more efficiently than soil based crops, with potential aerial productivities approaching 120T/ha/y, compared to 15T/ha/y for Miscanthus.

6.2  Microbial communities

  There are billions of microorganisms populating every niche of the Earth, many of which have untapped potential to help solve the global energy challenge. To grow in unusual environments, microorganisms have evolved unique metabolic strategies to extract energy from nutrients and sunlight to generate various potentially useful by-products. In many cases, these microorganisms function cooperatively in communities and consortia where their concerted activities perform functions that would not be possible in the absence of their partners.

  Consortia often contain diverse communities containing multiple strains of microbes. This has a number of benefits. Firstly, diverse communities tend to be more stable over long time periods. This is particularly important in bio-treatment processes, which generally operate in a continuous flow mode, frequently under unsteady state conditions and involve multiple elemental (biogeochemical) cycles. The value of using diverse microbial consortia is highlighted in the sewage industry where consortia consisting of bacteria, protozoa and fungi are applied in activated sludge for wastewater treatment and in anaerobic digestion for high strength organic feedstocks.

  The largest group of microscopic photosynthetic microbes are the microalgae. Microalgae have many advantages for cultivation as renewable energy crops over land based crops in the production of bioenergy; they have faster growth rates; they can be cultivated in poor quality or nutrient loaded wastewater and under difficult agro-climatic conditions; they require less land space and there is no fertiliser run-off; they can uptake toxic metals like chromium, cadmium and arsenic; by virtue of their relatively small sizes, they can be easily chemically treated and they contain no sulphur, are non-toxic and highly biodegradable. Costs associated with the harvesting and transportation of microalgae are relatively low, in comparison with those of other biomass materials from higher plants.

  The oldest group of photosynthetic microbes are the anoxygenic photosynthetic bacteria which comprise a large and heterogeneous group of organisms, brought together primarily because they all use light as an energy source in the absence of oxygen. These bacteria are mainly anaerobic organisms, and require a reduced compound as electron donor, such as H2S and simple organic molecules. Photosynthetic bacteria also produce hydrogen from organic compounds by an anaerobic light-dependent electron transfer process. Organic acids derived from either anaerobic digestion or fermentative hydrolysis or digestion[159] of organic waste/biomass provide ideal feedstocks for hydrogen production.

6.3  Harvesting

  Concentrating biomass for biofuel production is energy intensive. Therefore it is important to develop robust microbial consortia that have the ability to autoflocculate. Microorganisms can be present in bio-treatment processes as discreetly dispersed cells, as flocs, or as biofilms. The latter two are by far the most common and both flocs and films can be considered as matrices of naturally immobilised cells. More importantly, autoflocculation and biofilm growth provide a low energy means of harvesting the biomass from a liquid bulk. In the context of biofuels, low energy biomass harvesting is a fundamental prerequisite.

6.4  Photobioreactor (PBR)

  A PBR is a system that efficiently grows photosynthetic microbes, which are then used in various commercial applications. By providing efficient exposure to light, optimal temperatures, and pH levels, photobioreactors make viable the commercial production of algae.

  Figure 5: 5000 litre Biocoil PBR designed & constructed in UK by S. Skill (1993)[160],[161]

  During the 1980s, Professors John Pirt and David Hall of Kings College, London, were the early pioneers of photobioreactors and up until the late 1990s, the UK lead the world in PBR design and development.[162] PML now have the expertise[163] and infrastructure to reinstate the UK at the forefront of this field.

6.5  Photosynthetic Biofilms

  PSB systems are a relatively new technology for the growth of photosynthetic microbes and treatment of wastewater.[164],[165] They are inexpensive to construct utilising waste transparent plastic (PET: Polyethylene terephthalate) as the primary biofilm support matrix. PSB systems are capable of removing nutrients, heavy metals and hormone disrupting chemicals from wastewater in a low cost, single stage process, where the resultant biomass can be easily recovered and converted into biofuels.


  Plymouth Marine Laboratory (PML) is a Natural Environment Research Council (NERC) Collaborative Centre. As an internationally recognised interdisciplinary centre, PML is mission driven delivering a valuable, integrated approach to solving problems and providing solutions concerning the complexity of marine ecosystems and the unique bioresources they contain. PML is uniquely qualified to research and advise on many of the issues that form the debate on global change and sustainability in marine systems.

  PML has a strong core expertise in microbial chemistry, physiology and molecular biology (algae, viruses and bacteria). Key to the development of bioenergy within the UK, PML has world leading expertise in growing photosynthetic microbes on the large scale using Photobioreactor (PBR) Technology. Current research using PBR technology at PML is working towards the replacement of petroleum based products with a renewable resource and using CO2 from flue gas to promote growth and reduce CO2 emissions. The PBR technology PML is developing within these projects is directly applicable to large scale production of photosynthetic microbes for biofuels and biogas production. PML have a long term aim, building on core expertise, to build a centre of excellence in photosynthetic microbe biotechnology encompassing bioactives, biofuels, bioremediation and CO2 capture technology.

July 2007

151   Donohue & Cogdell (2006). Nature Reviews Microbiology 4, 800 Back

152   House of Commons Upper Waiting Hall: Photobioreactor Demonstration: 29 Jan-1 Feb 2007 Back

153 Back

154 Back

155   Parliamentary Office of Science and Technology, Postnote No. 282 April 2007 Back

156 Back

157   Banerjee, B, Sharma, Chisti Y, Banjeree UC. 2002: Critical reviews in Biotechnology 22(3) 245-279. Back

158 Back

159   Patent: Robinson & Skill, Means for Continuous Digestion of Organic Matter. US5637219 (1997) Back

160   National Geographic, March 1994 Back

161   New Scientist-Blooming Sewage, 2 October 1993 Back

162   Skill & Robinson (1991), Department of the Environment Select Committee. Evidence submission. Back

163   Patent: Skill & Robinson (2002), Photoreaction. US6370815 Back

164   Patent: Skill (1998), Culture of Microorganisms. WO9824879 Back

165   Patent: Skill & Robinson (2004), Purification of Contaminated Water. WO2004046037 Back

previous page contents next page

House of Commons home page Parliament home page House of Lords home page search page enquiries index

© Parliamentary copyright 2008
Prepared 19 June 2008