Welcome

 

This website is aimed to present the work currently undertaken by Fahad Alfahad as part of his final year Engineering Master's degree thesis at the University of Edinburgh. The project runs from September 2013 until May 2014. So far the project is in it's first stage of investigating the problem and reviewing the literature.

 

 

Problem Statement

The scientific community has come to a census that the global mean temperature of the earth will increase due to climate change effects. It is projected that a rise of 2C will occur by 2100 if mitigation measures are applied, and by 4C if no mitigation measures are taken. Mitigation of climate change is achieved by reducing Greenhouse gas emissions (GHG), which in practical terms suggests reducing fossil fuel emissions. The EU recognised this need to cut emissions and set GHG reduction targets such as 20% reduction by 2020 compared to 1990 levels.

 

Anaerobic digestion (AD) is used to produce biogas which formed mainly from methane and carbon dioxide. The biomethane could be used for Combined Heat and Power (CHP) plants or upgraded to natural gas specifications and hence injected into the gas grid. This could contribute to the energy security of many European countries that rely on imports for their energy supply.

 

Unlike other renewable energy sectors such as wind and solar, AD could be used to tackle another problem which is waste. In the UK various government efforts were undertaken to minimise the amount of organic biodegradable waste sent to landfills. Increasing the landfill tax was the main motive for households and industry alike to reduce the amount of waste sent to landfills. A shocking 12% of household food was wasted, which held a retail value of £12. Although AD would not have an effect on reducing the amount of waste produced, there is an obvious opportunity for AD to attract some of this waste especially with a landfill tax that will reach £80 per tonne by 2014/15. The main advantage of AD is that it has the potential of creating products such as biomethane and fertilisers from such organic waste. Organic fertilisers produced would preserve nutrients which could contribute into the sustainability of agriculture.

 

There are debates however regarding the economic viability of Anaerobic digestion. The capital costs of constructing AD plants are high and in a current economic climate AD would not develop without government incentives and ‘green’ loans etc. Another issue is the availability of feedstock over the year, as some types of feedstock could be seasonal. In the case of food waste this is not an issue, however consideration need to be take to the amount of food wasted in the future. In a recent statistic, over the period 2006-2010 food waste fell by 18.5% when food prices inflated by 20%.

 

Co-digestion could be a solution as it utilises the use of more than one type of feedstock in case of seasonality of such feedstock. Additionally co-digestion was shown on many occasions to increase the biomethane yield. Algae has been a relatively less researched type of feedstock and as macroalgae ‘seaweed’, could be sourced without the need to cultivate it was chosen for this study considering it as 'waste'. It is however important to enhance the biomethane potential of the co-digestion, which will be investigated in this project.