Any (re-)processing of materials will require energy. That raises issues of collection and transport, fuel efficiency and the ethics of global sourcing.  Unnecessary use of energy costs money and potentially contributes to climate change.  A European project, RECIPE: Reduced Energy Consumption In Plastics Engineering, aims to help the plastics processing industry to reduce their energy consumption.  The RECIPE best practice guide [i] provides a structured and practical approach to improving energy efficiency in the processing of plastics.

Reference

1. Best Practice Guide for Low Energy Plastics Processing from the European Community funded RECIPE project
    (supported by the Intelligent Energy Europe programme) contract no. EIE/04/153/S07.38646.

The generation of energy may contribute to degradation of the planets ecosystems.  The energy may come from a variety of sources, for example:

• nuclear
• James Lovelock [1] believes "nuclear power is the only source of energy that will satisfy our demands and yet not be a hazard to Gaia and interfere with its capacity to sustain a comfortable climate and atmospheric composition" [page 67] while "not recommending nuclear fission as the long-term panacea for our ailing planet or as the answer to all our problems [but] as the only effective medicine we have now" [page 11].
• Jack Harris [2] (using data from David Fleming in the June 2005 issue of Prospect)  states that "to make a significant impact on global warming nuclear would have to supply 100% of all the world's electricity requirements.  However, to do this, he calculates that the planets total quantity of viable uranium ores would last just six years".
1. The Sustainable Nuclear Energy Technology Platform
2. James Lovelock, The Revenge of Gaia: why the Earth is fighting back – and how we can still save humanity, Allen Lane, London, 2006. ISBN-13: 978-0-713-99914-3.
3. Jack Harris, Material matters: availability of uranium, Materials World, January 2006, 14(1), 56.
• hydrogen
• The generation of energy by combustion of hydrogen offers a clean energy source with emissions limited to water molecules, albeit that the production of hydrogen is energy intensive.
1. JOM Bockris, T Nejat Veziroglu and Debbi Smith, Solar Hydrogen Energy: the power to save the earth, MacDonald Optima, London, 1991. ISBN 0-356-20042-6.
2. T Nejat Veziroglu and Frano Barbir,Hydrogen Energy Technologies (UNIDO Emerging Technologies Series), UNIDO, Vienna, 1998.
3. D A J Rand and R M Dell, Hydrogen Energy - Challenges and Prospects, RSC Publishing, 2007. ISBN: 978-0-85404-597-6.
• fossil fuels
  • Burning coal without increasing global carbon dioxide levels is a major technological challenge.  The most promising "clean coal" technology involves using the coal to make hydrogen from water, then burying the resultant carbon dioxide by-product and burning the hydrogen.  The greatest challenge is bringing the cost of this down sufficiently for "clean coal" to compete with nuclear power on the basis of near-zero emissions for base-load power. [1].
  • Linc Energy Limited (Australia) has produced diesel from a demonstration coal-to-liquid (CTL) facility using underground coal gasification (UCG) [2].
  • "Capturing and storing carbon dioxide in a cost competitive and safe way is a significant challenge that could achieve significant reductions of CO₂ emissions in the atmosphere" [3].
  • The International Energy Agency Greenhouse Gas R&D Programme (IEA GHG) has a series of publications available to download including:
    natural releases of CO2, the Weyburn CO₂ Monitoring & Storage Project, Putting Carbon Back in the Ground, and Ocean Storage of CO₂.
  • The European Technology Platform for Zero Emission Fossil Fuel Power Plants (ZEP) has recognised that public acceptance of the role of CO₂ Capture and Storage (CCS) technology in mitigating climate change will be a prerequisite to its large scale deployment [4].
  • "Bamboo is the fastest growing canopy for the re-greening of degraded lands with stands releasing 35% more oxygen than wood trees.  Some bamboo can absorb up to 12 tons of carbon dioxide per hectare from the air" [5].
  1. "Clean Coal" Technologies, Briefing paper, Uranium Information Centre Limited Briefing Paper #83, May 2006.
  2. Mark Hull, Underground coal gasification, Materials World, January 2009, 17(1), 18.
  3. Ian Fells and John Horlock, Carbon capture and storage, Ingenia, June 2006, 27, 36-41
  4. A vision for zero emission power plants, EC DG for Research: Sustainable Energy Systems, Brussels, 2006. EUR 22043. ISBN 92-894-0545-7.
  5. M Doney, M Wroe and D Pratt, Top floor/Bamboo: the ecological wonder plant, Developments (DFID), 2006, 36, 25.
• biomass
  • The European Environment Agency [1] is currently assessing an environmentally-compatible primary bioenergy potential in Europe for 2010, 2020 and 2030. This work will provide input to the policy debates on both the upcoming Biomass Action Plan and proposed post-2010 renewable energy targets.  In a subsequent report, the EEA [2] has considered whether there is a limit to the quantity of biomass which can be grown without damaging the environment.
  • Biodiesel can use most animal fats and vegetable oils as raw materials [3].  The triglycerides are converted to methyl esters by transesterification with methanol. The fuel has a lower energy content than conventional diesel resulting in a 6% increase in volumetric fuel consumption.  A significant disadvantage is the ~10% yield by mass of glycerol (also known as glycerine) produced as a currently saleable by-product for use in resins, polyols, food, cosmetics, drugs, explosives, tobacco, paper making, adhesives and textiles.  Oversupply of glycerol can cause a sharp reduction in its price: of particular relevance for biodiesel production as the volumes of this by-product are high relative to most other production sources.
  1. How much biomass can Europe use without harming the environment?, EEA Briefing 02, European Environment Agency - Copenhagen, 2005.
  2. Tobias Wiesenthal, Aphrodite Mourelatou, Jan-Erik Petersen and Peter Taylor, How much bioenergy can Europe produce without harming the environment?, European Environment Agency report 2006/7, Copenhagen, 2006. ISBN 92-9167-849-x. ISSN 1625-9177.
  3. John Duncan, Costs of biodiesel production, Report for Energy Efficiency and Conservation Authority, May 2003.
  4. N El Bassam, Energy Plant Species - their use and impact on environment and development, Earthscan, March 1998. ISBN-13: 978-1-87393-675-7.
  5. Mary Walsh and Michael Jones, Miscanthus For Energy and Fibre, Earthscan, September 2000. ISBN-13: 978-1-9029-1607-1.
  6. Sjaak van Loo and Jaap Koppejan, The Handbook of Biomass Combustion and Co-firing, Earthscan, December 2007. ISBN-13: 978-1-844072491.
  7. F Rosillo-Calle, S Hemstock, P de Groot and J Woods, The Biomass Assessment Handbook - bioenergy for a sustainable environment, Earthscan, January 2008. ISBN-13: 978-1-84407-526-3.
  8. John Constable, Biofuels: the future?, Ingenia, March 2009, (38), 12-18.
• geothermal
  • The core of planet Earth is at a temperature of ~5000 degrees C, still cooling from its formation billions of years ago whilst insulated from the openness of space by the mostly solid mass of the earth's crust.  This heat can be tapped, as geothermal energy, to yield both warmth and power without polluting the environment.
  1. MH Dickson and M Fanelli, Geothermal Energy - utilization and technology, Earthscan, April 2005. ISBN-13: 978-1-84407-184-5.
  2. Karl Ochsner with introduction by Robin Curtis, Geothermal Heat Pumps - a guide for planning and installing, Earthscan, November 2007. ISBN-13: 978-1-84407-406-8.
• solar energy
[1]
• All known commercial renewable energy systems, with the exceptions of geothermal and tidal, are driven by the solar radiation which the earth receives [2].  This sub-section will focus on energy derived from the direct conversion of sunlight to heat and/or power.
• The maximum power density at the top of the atmosphere on the side of the earth directly facing the sun is ~1395 J/s.m² (2 cal/min.cm²) although this varies by about 7% primarily due to the changing distance between the earth and the sun [2].  Around 47% of this reaches the ground (24% by direct radiation, 17% by diffuse scatter from clouds and 6% by down-scatter from the atmosphere).  The balance is up-scattered by clouds (25%), absorbed by clouds (10%), absorbed by the atmosphere (9%) or up-scattered from the atmosphere (9%).
• Solar energy can be captured by design of buildings to trap the heat (passive solar) or focussing the energy onto fluids for heating of onto photoelectric cells for the generation of electricity.
• Ristinen and Kraushaar [2] state that "passive heating of buildings is generally not included in tabulations of solar energy usage because every building gains some solar energy through its windows, even those that are not directly south-facing [and hence] the actual importance of solar energy to the natural energy budget is understated in most accounts of energy sources".
• "Artificial photosynthesis is based on the concept of a dye analogous to chlorophyll absorbing light and thus generating electrons which enter the conduction band of a high surface area semiconductor film and further move through an external circuit, thus converting light into 'green' power" [3].  In consequence, biomass is essentially driven by solar energy.
1. Jeff Johnson, Power from the sun, Chemical and Engineering News, 21 June 2004, 82(25), 25-28.
2. RA Ristinen and JJ Kraushaar, Energy and the Environment - second edition, Wiley, 2006.  ISBN: 978-0-471-73989-0.
3. How It Works: Artificial Photosynthesis, http://www.dyesol.com/index.php?page=HowItWorks, accessed 12:26 on 08 March 2008.
• wind energy
• Wind turbines are becoming a feature of the landscape, but they do not always run smoothly!:
  • Wind turbine going wild and finally breaking, alternative view and slow motion sample (YouTube)
• By borrowing the best practices of composites blade design from the aerospace industry, wind turbine blade manufacturers can avoid costly errors and significantly reduce the time and cost of design, analysis and testing - while manufacturing stronger products with higher energy outputs.
  • Webcast: Discover how best-practices learned in the aerospace industry can help you design better blades, faster and more cost-effectively.
1. European Wind Energy Association, Wind Energy - The Facts: a guide to the technology, economics and future of wind power, Earthscan, London, March 2009. ISBN 978-1-84407-710-6.
2. MOL Hansen, Aerodynamics of Wind Turbines - second edition, Earthscan, December 2007. ISBN 978-1-84407-438-9.
3. Robert Harrison, Erich Hau and Herman Snel, Large wind turbines: design and economics, John Wiley & Sons, 2000. ISBN 978-0-471-49456-0.
4. Jeff Johnson, Blowing green, Chemical and Engineering News, 24 February 2003, 81(8), 27-30.
5. GR Kirikera, M Sundaresan, F Nkrumah, G Grandhi, B Ali, SL Mullapudi, V Shanov and M Schulz, Wind Turbines, In C Boller, F-K Chang and Y Fujino (editors), Encyclopedia of Structural Health Monitoring, John Wiley & Sons, Chichester, 2009.
6. JF Manwell, JG McGowan and AL Rogers, Wind Energy Explained, John Wiley, Chichester, 2002.  ISBN 0-471-49972-2.
7. John Walker and Nicholas Jenkins, Wind Energy Technology, John Wiley, Chichester, 1997.  ISBN 0-471-96044-6.
8. BB Nalukowe, J Liu, W Damien and T Lukawski, Life Cycle Assessment of a Wind Turbine, KTH School of Architecture and the Built Environment, 22 May 2006.
9. Some additional references.
• hydroelectric energy
• The earth's natural water cycle provides rain (and on higher land seasonal snow and hence runoff when it melts). The water flows downstream via streams, rivers and lakes and can be contained by dams en route. This head of water can then be channelled to a turbine which generates electricity.
• See also Dinorwig Power Station under energy storage and transmission below.
1. West Webburn River: 90kW of renewable electricity is generated on Dartmoor and excess sold to the National Grid. http://www.waterleat.co.uk/
• wave energy
• Wave energy is due to movements of water near the surface of the sea [1]. Waves are formed when wind blows over the water surface, making the water particles adopt circular motions. This kinetic energy is determined by the speed and duration of the wind, the length of sea over which it blows, the depth of water, the sea bed conditions and also any interactions with the tides.
• The bioWAVE^TM wave energy system [2] has long vertical blades which sway back and forth in response to oscillating wave forces. This motion is partially resisted by an electrical generator mounted at a pivot near the sea floor. In excessive wave forces, the device lies flat against the seabed to avoid damage.
1. Guide to Marine Energy: an overview of marine energy generation, Marine Energy Challenge News issue 1, accessed 13:18 on 04 April 2006.
2. Biomimetics To Harness Ocean Power, Warren Centre for Advanced Engineering, November 2006.
3. Guide to Marine Energy: the description of real seas and how wave characteristics affect device design, Marine Energy Challenge News issue 2, accessed 13:40 on 04 April 2006.
4. Jeff Johnson, Power from moving water, Chemical and Engineering News, 04 October 2004, 82(40), 23-30.
5. Marine Renewables: Wave and Tidal Stream Energy Demonstration Scheme, DTI Energy Group, January 2005.
6. T W Thorpe, A Brief Review of Wave Energy, ETSU Report ETSU-R120 for The UK Department of Trade and Industry, May 1999.
• ocean thermal energy conversion (OTEC)
  • Water near the surface of (sub-)tropical seas is kept at higher temperatures than water at greater depths or at higher latitudes.  Some effort has been dedicated to trying to harness this temperature difference.
• tidal barrage
  • Tidal energy occurs due to large movements of water in the sea. As tides flow and ebb (come in and go out respectively), water near the coast is raised and lowered and the potential energy of this tidal range can be exploited [1]. The environmental and ecological impacts of such systems are complex.
  • The largest tidal barrage power station is La Rance in France where 24 x 10 MW turbines extract power from a 22 km² basin with a tidal range up to 8 m. 
  1. Guide to Marine Energy: an overview of marine energy generation, Marine Energy Challenge News issue 1, accessed 13:18 on 04 April 2006.
  2. Jeff Johnson, Power from moving water, Chemical and Engineering News, 04 October 2004, 82(40), 23-30.
  3. Marine Renewables: Wave and Tidal Stream Energy Demonstration Scheme, DTI Energy Group, January 2005.
  4. UK Hydrographic Office, Admiralty Tide Tables, 2003. http://www.ukho.gov.uk/admiralty_tide_tables.html.
• tidal stream
  • Tidal-stream energy is the direct extraction of kinetic energy from the motion of water in naturally occurring tidal currents in the sea.  Black & Veatch [2] suggest that the UK resource may be about half the entire European resource (and one of the most concentrated tidal stream resources in the world) which could generate 22 TWh/year without causing significant changes to flow momentum or significant environmental impacts.
  • The bioSTREAM^TM tidal current system mimics the shape and motion characteristics of highly efficient Thunniform-mode swimming species (such as shark and tuna) but is fixed in a moving stream and converts the motion of the fluid into energy to drive the device against the resisting torque of an electrical generator.
  • Wood [3] has presented a useful review of composites in tidal energy devices.
  1. Guide to marine energy: the nature of the tidal stream resource and aspects of generation device design, Marine Energy Challenge News issue 3, accessed 13:15 on 04 April 2006.
  2. Focus on tidal stream: a summary of work by Black & Veatch Consulting on the tidal stream resource, Marine Energy Challenge News issue 1, accessed 13:20 on 04 April 2006.
  3. K Wood, Composites tap tide energy, Composites Technology, October 2010, 16(5), 28-36.
     Wave-energy conversion (side-bar article accompanying the above).
  4. Biomimetics To Harness Ocean Power, Warren Centre for Advanced Engineering, November 2006.
  5. Jeff Johnson, Power from moving water, Chemical and Engineering News, 04 October 2004, 82(40), 23-30.
  6. Marine Renewables: Wave and Tidal Stream Energy Demonstration Scheme, DTI Energy Group, January 2005.
  7. UK Hydrographic Office, Admiralty Tidal Stream Atlases, 2003. http://www.ukho.gov.uk/admiralty_tidal_stream_atlases.html.

A more complete description of the relative merits of each option is beyond the scope of this module.  A number of authors [1, 2] have considered life-cycle assessment for the energy sector.

1. Malgorzata Góralczyk, Life-cycle assessment in the renewable energy sector, Applied Energy, July-August 2003, 75(3-4), 205-211.
2. S Walker and R Howell, Life cycle comparison of a wave and tidal energy device, Proc. IMechE Part M: Journal of Engineering for the Maritime Environment, November 2011, 225(4), 325-337

Relevant technologies associated with energy generation include:

• carbon capture and storage
• Fells and Horlock [1] have reported that "capturing and storing carbon dioxide in a cost-competitive and safe way is a significant challenge that could achieve large-scale reductions of CO₂ emissions into the atmosphere.
• Hester [2] has described the current options and the potential of future CCS strategies.
• Pervaiz and Sain [3] have shown that the use of natural fibre reinforcements in thermoplastic matrix composites has potential as a "sustainable" sink for atmospheric carbon dioxide.
1. Ian Fells and John Horlock, Carbon Capture and Storage, Ingenia, June 2006, (27), 36-41.
2. RE Hester and RM Harrison, Carbon Capture and Storage, RSC Books, 2009. ISBN-13: 987-1-84755-917-3.
3. Muhammad Pervaiz and MM Sain, Carbon storage potential in natural fiber composites, Resources, Conservation and Recycling, November 2003, 39(4), 325-340.
4. John Oakey, Containing carbon — carbon capture and storage, Materials World, October 2008, 16(10), 26-27.
5. James Meadowcroft and Oluf Langhelle (editors), Caching The Carbon: the politics and policy of carbon capture and storage, Edward Elgar Publishing Limited, Cheltenham, 2009. ISBN 978-1-84844-412-6.
• energy storage and transmission
• Dinorwig Power Station (1728 MW), commissioned in 1984, is the largest pumped storage hydroelectric scheme of its kind in Europe [1]. It consists of Europe's largest man-made cavern, with 16 km of underground tunnels, deep below Elidir mountain in Wales.  Off-peak electricity is used to pump water from the lower reservoir up to Marchlyn Mawr reservoir (location map and photograph).  The six reversible pump/turbines are capable of reaching maximum generation capacity in less than 16 seconds.
1. Dinorwig Power Station Llanberis, First Hydro Company, undated, accessed 11;25 on Saturday 16 February 2008.
2. Bent Sørensen, Renewable energy conversion, transmission and storage, Academic Press, November 2007. ISBN-13: 978-0-12-374262-9.
3. EUR 21240 European CO2 Capture and Storage Projects (Sixth Framework Programme Project Synopses), European Commission, Luxembourg, 2004. ISBN 92-894-8002-5.
4. EUR 22574 CO2 Capture and Storage Projects (Project Synopses), European Commission, Luxembourg, 2007. ISBN 92-79-03724-2.
• Trans-Mediterranean Renewable Energy Cooperation (TREC)
• TREC is an initiative to campaign for the transmission of clean power from deserts throughout Europe, the Middle East and North Africa. It was founded in 2003 by The Club of Rome, the Hamburg Climate Protection Foundation and the National Energy Research Center of Jordan. TREC aims to boost the generation of electricity and desalinated water by solar thermal power plants and wind turbines in the Middle East and North Africa (MENA) and to transmit the clean electrical power via High Voltage Direct Current (HVDC) transmission lines throughout those areas and from 2020 into Europe.

Other resources on these issues include:

• David Mackay, Sustainable Energy - without the hot air, UIT Cambridge Limited, 2009. ISBN 978-0-9544529-3-3 (paperback), ISBN 978-1-906860-01-1 (hardback).
• VVN Kishore, Renewable Energy Engineering and Technology: principles and practice, Earthscan, London, April 2009. ISBN 978-1-84407-699-4.
• RA Ristinen and JJ Kraushaar, Energy and the Environment - second edition, Wiley, 2006.  ISBN: 978-0-471-73989-0.
• Janet Wood, Local Energy: Distributed Generation of Heat and Power, IET Publishing, Stevenage, 2008. ISBN-13: 978-0-86341-739-9.
• ETDE: Energy Technology Data Exchange (also known as the Energy Information Library)
    ..  free access to almost 4 million articles and papers on energy research and technology.
• DTI Energy Policy and Strategy
• NERN: National Energy Research Network
• UK Energy Research Centre  Energy Research Atlas
• Cornwall Sustainable Energy Partnership

... and for climate change the following may be of use:

• California Climate Change Extension
  • Interview with Dan Kammen on Alternative Energy
  • Interview with Dan Cayan on Climatology
  • Interview with Kelly Redmond on Climatology
  • Interview with Michael Hanemann on Economics
  • Interview with Dan Sperling on Transportation