Life Cycle Analysis
The Green Building Handbook’s Product Tables present a summary of the environmental impact of each product covered in an ‘easy-to-read’ format. A circle in a column will indicate that we have discovered published comment on a particular aspect of a product’simpact. The larger the circle the worse an environmental impact is thought to be (in the opinion of the author). Marks on each Table will only indicate poor records relative to other products on the same Table.
Every mark on the product Table has a corresponding entry in the Product Analysis section, which explain why each mark was made against each particular product, Life Cycle or ‘cradle-to-grave’ analysis of a product’s environmental impact is a relatively new, and still contentious field. It is accepted that it should involve all parts of a product’s life; extraction, production, distribution, use and disposal. The Green Building Handbook’s Product Tables amalgamate these for ease of presentation, so that issues involving the first three, extraction, production and distribution are presented in the nine columns grouped under the heading
‘Production’; the last two, use and disposal, are presented together under the heading ‘Use’.
Less well accepted are the more detailed headings under which life cycle analysis is performed. Those we have used are based on those used by other LCA professionals, but developed specifically for this particular use—presenting information about building products in a simple table format.
The most fundamental problem with LCA is in trying to come up with a single aggregate ‘score’ for each product. This would entail trying to judge the relative importance of, for example, 50g emission ozone depleting CFC with a hard-to- quantify destruction of wildlife habitat. in the end the balancing of these different factors is a political rather than scientfic matter.
Key to Product Table Ratings
The environmental impacts of products are rated on a scale from zero to 4 under each impact category. A blank represents a zero score, meaning we have found no evidence of significant impact in this category. Where a score is assigned, bear in mind that the scores are judged relative to the other products on the same Table.
The following symbols represent the impact scale: ... worst or biggest impact ....
next biggest impacte ... lesser impact ... smaller but significant impact [blank] no significant impact
Key to product Table Ratings
The environmental impacts of products are rated on a scale from zero to 4 under each impact category. A blank represents a zero score, meaning we have found no evidence of significant impact in this category. Where a score is assigned, bear in mind that the scores are judged relative to the other products on the same Table.
The following symbols represent the impact scale: ... worst or biggest impact ....
next biggest impact ... lesser impact ... smaller but significant impact [blank] no significant impact
Unit Price Multiplier
This column shows the relative cost of the different options listed on the table based on a standard unit measure.
Production
This group heading covers the extraction, processing, production and distribution of a product.
Energy Use
More than 5% of the UK’s total energy expenditure goes on the production and distribution of building materials. This energy is almost always in the form of non- renewable fossil fuels.
In the absence of information on other aspects of a product’s environmental impact, energy use is often taken to be an indicator of the total environmental impact.
Resource Depletion (biological)
Biological resources, whether of timber in tropical forests or of productive land at home, can all be destroyed by industrial activity. These can only be counted as renewable resources if they are actually being renewed at the same rate as their depletion.
Resource Depletion (non-biological)
Non-biological resources are necessarily non-renewable, and so are in limited supply for future generations, if not already. These include all minerals dug from the ground or the sea bed.
Global Warming
Global warming by the greenhouse effect is caused chiefly by the emission of carbon dioxide, CFCs, nitrous oxides and methane.
Ozone Depletion
The use of CFCs and other ozone-depleting gases in industrial processes still continues despite many practicable alternatives.
Toxics
Toxic emissions, to land, water or air, can have serious environmental effects, none of which can ever be completely traced or understood.
Acid Rain
A serious environmental problem, causing damage to ecosystems and to the built environment. Caused mainly by emissions of the oxides of sulphur and nitrogen.
Photochemical Oxidants
The cause of modern-day smog, and low-level ozone, causing damage to vegetation, material and human health. Hydrocarbon and nitrogen oxide emissions are chiefly responsible.
Other
No ‘check-list’ can ever cover all aspects of enviromental impact. See the specific Product Analysis section for an explanation of each case under this heading.
Use
This group heading covers the application at the site, the subsequent in-situ life and the final disposal of a product.
Energy Use
Nearly 50% of the UK’s total energy consumption is in heating, lighting and otherwise serving building. The potential impact, and therefore potential savings, are enormous.
Durability/Maintenance
A product that is short lived or needs frequent maintenance causes more impact than one built to last.
Recycling/Reuse/Disposal
When a building finally has to be altered or demolished the overall environmental impact of a product is significantly affected by whether or not it can and will be re-used, repaired or recycled, or if it will bio-degrade.
Health Hazards
Certain products cause concerns about their health effects either during building, in use or after.
Other
Again no list like this can ever be complete. See the specific Product Analysis section for an explanation of each case.
Alert
Anything that we feel deserves special emphasis, or that we have come across in the literature that is not dealt with elsewhere, is listed here on the Table.
Energy 4
4.1
Scope of this Chapter
This chapter looks at the environmental impact of the choice of energy supply for space and water heating in buildings. Both conventional fossil-fuel energy and alternative renewable sources are considered, together with the practicalities of alternative renewable sources. Different types of equipment (e.g. boilers, generators, etc.) are not covered in any depth.
ªThe last two decades have witnessed scientific consensus that the burning of fossil fuels has to be capped and eventually reduced.º
(M K Tolba (3))
4.2 Introduction
Global warming, the rise in global average air temperatures caused by increased emission of greenhouse gases, is likely to cause such changes in climate, weather
patterns and sea levels that the lives of everyone on earth will be affected. Its primary cause, though there are others, is the CO2 emissions from the burning of the fossil fuels—coal, oil and gas.
These fossil fuels are themselves in limited supply. Optimistic estimates for world crude oil production expect that it will peak within the next five years, and from thereafter be in decline.1 We cannot rely, however, on the oil wells (or gas wells or coal mines) drying up in time to stop global warming. Action to reduce the use of fossil fuels must begin now.
Why Me?
As a building designer, specifier or in any other capacity responsible for the choice of heating systems in a building, you have more opportunity to do something about global warming than anyone except the politicians and energy multinationals. The use of energy in buildings in the UK is responsible for just over half of the country’s total CO2 emissions, twice as much as that from industry or transport.1,12 40% of UK energy is expended on heating buildings,7 25% on heating our homes.12 If any impact is to be made on global warming, drastic changes will have to be made in the way we heat our buildings. (See below, ‘A safe level for CO2 emissions?’) To put it in perspective, the embodied energy of building materials, a key issue in other chapters, is perhaps ten or a hundred times less important for global warming than burning fuels for heating buildings.14
A safe level for CO2 emissions?
One estimate reckons that cuts in CO2 emissions of around 75% must be made in the industrialised countries if the effects of global warming are to be arrested.14 According to Friends of the Earth, “no definitive answer can be given to the question of what levels of reductions in emissions [of greenhouse gases] will be required to keep future climate change within tolerable limits…It is clear…that a short term commitment of all industrialised nations to carbon dioxide reductions in the order of 25–50 per cent by y ear 2005 is needed if the risks of climate change are to be minimised.”21 That is just in the next eight years.
It must be emphasised that the science behind these figures is still subject to much debate, but in view of the probable threat, it would be prudent to adopt the precautionary principle and act to substantially reduce CO2 emissions.
The governments of the most progressive countries on this issue (e.g. Austria, Germany and New Zealand), are currently committed to around 20–25%. In the longer term, cuts would have to go further—45–55% by 2050, possibly 80–100%
by 2100. These figures also assume reductions of other greenhouse gases, and an end to deforestation.
Friends of the Earth’s medium term view is that “an appropriate initial CO2 reduction target for an industrialised country such as the UK would be at least 30 per cent by 2005 on 1990 levels.”20 Given the slow rate of change of the nation’s building stock, an achievement of that sort of reduction in the energy used by
buildings by that date, would necessarily involve improvements to existing buildings.
Even if all new buildings were designed and built for zero CO2 emissions, this would not, on its own, be enough to meet this target.
The Truth About Being Economical
The supply of energy can either be capital intensive, as in the case of wind power, where a high initial investment is needed, but the running costs are minimal, or expenditure intensive, as is the case for most fossil fuels where the running costs (fuel) dominate. It would seem to be common sense that for any long-term project (such as heating a building) capital intensive, low-running-cost options should always work out cheaper in the long run, and therefore be generally the most widely used.
That this is not the case is due, in part, to the short termism of the suppliers of capital. It is also due to the effects of judging these costs against the benchmark of the marginal cost of using the equivalent amount of the cheapest fuel, usually gas or oil, and the fact that the true costs of these options are seriously underrated if their full environmental costs were also to be included.36
What People Want
Energy is not, of course, what people want. They want the services it can provide:
comfort and warmth; hot water for washing; light to see by.7 This is shown in the statistics for comfort standards in dwellings. From 1970 to 1991 average temperatures in dwellings rose from 12.83° to 16.66°C, but there was no great increase in consumption of energy for space heating. It came about due to the increased use of more efficient appliances— dwellings with central heating rose from 34% to over 80%.11
A BRE study has shown that proven technologies could reduce CO2 emissions from the energy use of existing dwellings by 35% without reducing comfort levels.
Of these improvements, two thirds were achievable by increased insulation, one third by increased appliance efficiency. (The effect of switching fuels was not included.) Over two thirds would actually save money.12
Any Answers
The answer to global warming and resource depletion is simple. Firstly energy requirements should be minimised by good design. Then, wherever possible we should use solar-based renewables, such as sun, wind or biomass, rather than fossil fuels, and where we can’t, the efficiency with which we use fossil fuels should be maximised.35 This ‘wherever possible’ is important. A key strategy for sustainable development is the appropriate use of resources and technology. An ideal policy† would, until realistic replacements arrive, limit the use of fossil fuels thus: oil (as
petrol, diesel etc.) should be reserved for mobile transport fuel; gas for high temperature industrial
The Political Climate
Under the United Nations Framework Convention on Climate Change, the UK is committed to stabilising greenhouse gas emissions “at a level that would prevent dangerous anthropogenic interference with the climate system”. Also, as a developed country, the convention commits us to returning emissions of each greenhouse gas to 1990 levels by 2000. European Environment and Energy ministers also agreed that the community as a whole should stabilise CO2
emissions by 2000 at 1990 levels.
The UN commitment is the strongest, and is aimed at sustainability. Even if industrialised nations stabilise at 1990 levels, global warming could still rise at twice the rate considered tolerable by sensitive ecosystems and vulnerable populations.
processes; coal for electricity generation for lighting, communication, stationery machinery and tracked transport.19 Nowhere does the heating of buildings come into this list, apart from maybe some surplus heat from the power station via a district heating system. Crucially, realistic replacements are here already for heating buildings, but not so for the other uses of fossil fuels. It therefore falls on the building sector to take on more than its ‘fair share’, and to take the lead in renouncing fossil fuels.
ªOn the scale of human history, the era of fossil fuels will be a short blip.º (Meadows et. al. (35))
4.3 Best Buys
or What You Can Do¼
Remember the cheapest form of energy is conservation—minimise energy requirement by good design.
Passive solar design is by far the best environmental option for space heating.
Don’t leave it to the end to ‘bolt on’ a heating system, include it from the beginning of the design stage (especially so with passive solar).
† N.B. This strategy only deals with global warming and resource depletion issues—
localised pollution effects from fossil fuel burning are a further complicating factor.
Active solar for water heating is now a proven technology, and though expensive, can give worthwhile contributions to water heating.
Maximise use of renewable sources wherever possible—e.g. a wood stove for backup heat in the winter.
If you must use a backup fossil fuel, use gas (or LPG if not on mains) and a condensing boiler, with good controls and meters.
District or community heating systems offer potential for economies of scale that make renewables such as active solar for space heating, or even wind and biogas, worthwhile.
ªWe will inevitably achieve 100% reliance on renewable sources eventually. All that we can determine is how quickly we move towards the goal.º13
4.4 Product Analysis
4.4.1 Fossil Fuels
(a) Coal Resource Life
Estimates for the life of the world’s coal reserves vary between around 200 to 500 years.1,35 It is thus by far the most abundant fossil fuel. Nevertheless, it is still a finite resource, and as the other fossil fuels run out, is likely to be used in increasing amounts, so its lifetime could be much shorter.
Global Warming
Burning coal releases more CO2 than other fossil fuels,6,11 and the deep mining of coal releases methane, another potent greenhouse gas, to the atmosphere.3,22
Acid Rain
Coal naturally contains sulphur in varying amounts depending on the grade of the coal and where it comes from. It is this sulphur content that gives rise to SOx the chief acid rain-forming gases. Coal burning is the major cause of acid rain, causing around 75% of SO2 emissions in the UK.22
Photochemical Smog
Coal burning is responsible for significant quantities of oxides of nitrogen, hydrocarbons and carbon monoxide, the photochemical smog gases.3,22,34
Particulates
The particulate emissions from coal burning were well known in British cities before the Clean Air Acts cleaned up the famous smogs. Particulates from coal burning are around 3 times the quantity as from oil.3,34
Toxics
Coal smoke contains a wide range of harmful chemicals, some of which are carcinogenic.16,33 Trace amounts of radionuclides (radioactive elements) are present in coal, and are released on combustion.3
Risks
The occupational risks of deep coal mining, both to the miners’ health and from accidents and cave-ins are well known.33 The use of open fires in the home also increases the risk of house fires.33
Other
The impact of coal mining on the local environment can be considerable:
impacts include land use for mines and spoil heaps; subsidence; disturbance of habitats by open cast (surface) mining; pollution of water courses and tables by acid and salted mine drainage, water wash treatment and runoff from storage heaps; transport of coal by road; dust emissions; and visual impact.3,5,22
(b) GasÐNorth Sea
Resource Life
Known reserves of natural gas, at current consumption levels, may last for around 60 years.35 Some commentators believe that, given the present growth in discoveries, gas will be available for the next 100 years and that “No real crisis in supply is imminent".36 Others argue that the current growth in the use of natural gas will just about balance out the expected new discoveries, leaving a resource life still around the 60 year mark.35 Natural gas is being used at increasing rates, because it is currently very cheap, and is seen as a ‘clean’ fuel.
Global Warming
Burning of natural gas creates the least amount of CO2 per unit of heat than for any other fossil fuel, but it is still a considerable amount—around 60 kg.CO2/GJ.11 Moreover, natural gas (methane) is itself a potent greenhouse gas, so leaks in the system anywhere from the drilling rig to the domestic piping also contribute directly to global warming.3,22
Acid Rain
Natural gas contributes very little to acid rain: SO2 emissions are virtually zero;
and NOx emissions are very small compared to other fossil fuels.34
Emissions of the Photochemical Smog gases, Particulates and Toxics are likewise low from the combustion of natural gas.34
Risks
The chief risks associated with gas use are explosions (either at point of use or production), and storm or diving accidents at off-shore production platforms.33
Other
The local impacts of gas extraction are similar to those for oil extraction, with pipelines being the major source.
(c) LPG
LPG or bulk propane is a by-product of oil refining,17 thus its impact rating for extraction is the same as that of oil (see below). On combustion, LPG is almost as clean as methane (natural gas), but gives off slightly more CO2.6
(d) Oil Resource Life
Known oil reserves will last only about 30 years33 with expected discoveries increasing this figure by perhaps another 10 years.35 The most optimistic estimate is for about 70–80 years1 before it is all gone, but prices will surely rise long before then to make it much less of an attractive economic proposition for ‘low-grade’
use such as heating. UK production from the North Sea has already peaked, and has been declining since 1985/6.36
Global Warming
The emissions of CO2 from oil combustion lie between those of coal and gas at around 80 kg.CO2/GJ.11 Methane is often also released or flared off during oil extraction, further contributing to the greenhouse effect.
Likewise with emissions causing Acid Rain and Photochemical Smog, and with Particulates and Toxics emissions, oil combustion falls between coal and gas.34,3,22 Some further toxic hydrocarbons, such as benzene, are also emitted during the oil extraction process.3
Risks
Occupational risks in oil production are mainly concerned with safety on oil rigs, including blowouts and fires (e.g. Piper Alpha).
Other
Leaks and spillages of oil, either routine or accidental, also cause concern, as does the impact of pipelines and refineries.3
(c)
Electricity (national grid)
In the UK, energy distributed over the national grid as electricity comes from three main sources:
Energy Sources of UK electricity supply22
Coal 68%