Using wastes continued: urban waste

There are other types of wastes apart from agricultural ones, which were not included in the reports mentioned in my previous posts. These are urban wastes, such as municipal solid waste and excreta which can be used to produce gaseous fuel, and waste cooking oil, which can be used as transport fuel too (SECO, 2008).

The production of gaseous fuel means that the methane which the landfill material produces is initially not released into the atmosphere, thus decreasing the emissions overall, even if some GHGs are emitted eventually. This is important, as municipal solid waste, for example, is the biggest anthropogenic source of methane, a highly potent gas contributing to global warming and to air pollution (SECO, 2008). Turning this harmful gas into energy is therefore said to reduce odours, help the environment and generate a profit. It also means that the solid residues left can be used as a fertilizer afterwards, meaning that the impacts of such biofuels on other activities, such as agriculture, is negligible in this case (SECO, 2008).

IEA (2008) found that using the biogas to produce heat and electricity is more economic than using it to power cars, as it does not require processes such as purification. SECO (2008) uses the example of powering homes in Texas to show the amount of biofuel this waste would be able to produce. It shows that if the 70 biggest landfills there turned the biogas released into energy, 100 000 households in Texas would be powered. However, due to few economic incentives, this technique did not start to be employed until recently, when the land area available for landfills started to become scarce (SECO, 2008).  

Butterworth (2009) suggests that as for incinerating solid municipal waste directly as a biofuel, it is not a sufficiently environmentally-friendly activity, as it produces carbon dioxide during incineration. Instead, he suggests that after the gas has been collected, the remaining solid matter should be utilized as a fertilizer for biofuel cultivation: this will save on the emissions that are produced during synthetic fertilizer manufacturing (Butterworth, 2009). Butterworth suggests that in this way, 600 American households will be able to fertilize enough land to result in 1 te of biofuel from rapeseed. This technique has begun to be utilized on a small scale already e.g. the Lincolnshire Bates Farm (Butterworth, 2009). Similarly, as mentioned in a previous post a while ago, other urban wastes, such as the gypsum from constructing sites has been proposed to be used as a fertilizer (UNCC, 2010).

However, such biofuel from waste does not seem to be included in the calculations of how much biofuel it will be possible to produce. This leads to the conclusion that these calculations potentially significantly underestimate the actual figures, thus contributing to the already substantial uncertainty regarding the matter.