The project initially started with a literature review. This was to research the current state of the art, with regard to carbon neutral communities, and to define the project area. It was also to determine which techniques and approaches were possible and how effective they might be.
Most attempts at a carbon neutral community have been undertaken in a rural setting. This often allows more access to renewable technologies due to the surrounding landscape being unaffected by built up areas. The population density is also less which, in turn, means the energy demand density is less. In effect, there is less demand and a more abundant renewable energy supply when compared to an urban setting. There are also more suitable sites for trees, which absorb CO2. Many rural communities attempting such a scheme also have greater access to capital as they are in prosperous areas and have access to grants. The most obvious, and widely adopted choice, is upgrading insulation and installing a wind turbine. Any profit from the wind turbine is paid back into the community. Therefore, these communities can be benefitting economically but only offering a small contribution in carbon emissions due the relatively small generation.
There are some examples of island communities attempting carbon neutral status, such as Samso in Denmark. In this instance, consumption has been reduced, efficiency has been improved and sustainable generation has been installed. Islands have the added resources of wave, tidal and offshore wind at their disposal, however, this is likely to be balanced by the added energy required for ferry transport.
The only large scale project that was found during research was that of the proposed Masdar City. The design is expected to incorporate a vast solar array outside of the city in the desert. It also intends to utilise active as well as passive building design to achieve air cooling within the city, by using devices such as active solar shades. The design of the city is such that it is compact to minimise transport and takes full advantage of the local climate. It is intended to be entirely self sufficient.
Many developments have been made into producing new build zero carbon buildings. An example of such a development would be BedZed in London which claims to have zero carbon homes. However, with the majority of house stock already in existence, there appears to be a greater gain to be made from extensive retrofitting as this process does not incur the large embodied energy of new builds.
Retrofitting does encounter some challenges however as some buildings are designated as ‘Hard to Treat’. Examples of such buildings would be high rise housing and buildings with solid walls. A building over 3 floors high may present issues of accessibility when retrofitting, and solid walls limit the ability of extra insulation.
The largest demand for energy in most UK housing appears to be space heating. There are two main methods of reducing the carbon emissions of this demand. The first is to reduce the demand itself, with better insulation, draught-proofing and efficient boilers. The other method, which can be applied in parallel, is to reduce the carbon emissions of the source of energy with a switch to biofuels, or heat recovery.
Social and behavioural issues must be taken into account when considering the possibility of a carbon neutral community. The attitudes of community members must correlate to achieve the desired outcome and this may involve a lifestyle change of some sort. However, for the purposes of this project, any changes have been addressed under possible education and market transformation, and the focus will remain on the implementation of engineering solutions.
Often, one of largest consumers of energy is industry and is usually not considered in existing attempted carbon neutral communities due to the focus on rural locations. Most industrial processes require or produce some form of heat, and this heat could be recycled more effectively through schemes such as district heating to nearby residences.
There are many forms of renewable generation and to be a successful carbon neutral community would require the utilisation of multiple sources. With multiple sources the intermittency of many renewable technologies can be factored out. Rural communities have greater access to a variety of renewable energy sources. Within an urban community, there is a greater degree of resourcefulness required to obtain sources of generation. One such area would be the recycling of waste to produce energy. The use of spent grain from a brewery to be used as fuel in a biomass plant is one such possibility. Another area of interest that was found is use the use of human or food waste in an anaerobic digester to produce biogas. Such a process offers considerable opportunity when coupled with the population density of urban communities.
There are various methods of carbon capture, with the simplest being the photosynthesis process of plants and trees.
Synthetic trees are another possible method of carbon capture that is still under development. These synthetic trees use a filtering process to extract carbon dioxide molecules from the air so that it can be stored or utilised elsewhere. Although initial studies show it to be effective at capturing carbon, the need for a destination for the carbon leaves issues to be resolved.
Most attempts at carbon neutral communities fail because they concentrate on one area to improve, usually the cheapest and easiest method. A much wider approach is needed, one which incorporates multiple functions within a community.