Food for thought: How to reduce reliance on fossil fuels by utilising brownfield sites and food waste

By Lee Ollerenshaw



It is now clear that climate change is no hoax. The impacts on our coral reefs are widely documented, as are the negative effects on our bee populations. But these only scratch the surface of what climate change is doing to the planet. The frequency of extreme weather events, such as floods and droughts, is increasing around the world [1]. Events such as these are warnings about how severe the consequences of climate change can be. The Earth’s natural processes are being thrown off-balance, nature is suffering and humanity is next unless actions are taken. The average rate of global temperature increase is now 0.18°C per year and seven of Earth’s ten warmest years on record have occurred post-2013 [2]. Most recently, 2020 has tied 2016 to be the hottest year on record and current predictions suggest temperatures will keep rising unless there is intervention. Intervention requires global unison. That is why climate change conferences such as COP26 are vital for the future. However, creating a solution to climate change that everyone agrees on is extremely challenging. A requirement of every country is energy. Current methods of generating energy via fossil fuels are detrimental to the planet and a major driver of climate change. Fossil fuels are also a finite resource, so a more sustainable method is required. Additionally, the EU have collective objectives for tackling soil pollution [3] and reducing greenhouse gas emissions [4]. The idea proposed in this piece would help to address all of these problems, allowing the generation of large amounts of energy whilst utilising already available brownfield sites and food waste.

Fossil fuels

As is widely known, the use of fossil fuels is causing extreme damage to our planet, yet they are still the most used energy resource [5]. 15 billion metric tonnes of fossil fuels are burnt each year [6]. As a result, approximately 36 billion tonnes of carbon dioxide (CO2) are released into the atmosphere [7].  Fossil fuels make up around 84% of all energy resources, with 27% being coal, 33% oil and 24% gas [8]. In 2019, these fuels produced approximately 137,000 TWh out of the 162,000 TWh produced worldwide from all sources [9]. This market share needs to be reduced in order to move to carbon neutral energy production. 


Biofuels show great potential for carbon neutral energy production. In 2017, renewable energy was 17.7% of the gross final energy consumption globally, with biofuels accounting for 70% of the renewable energy generated [10].  The main requirement for the growth and production of biofuel is land. According to the World Bioenergy Association (2019), agriculture land accounts for 37% (4.8 billion hectares) of global available land area. 70% of agriculture land is under permanent pasture and meadows, mostly for cattle rearing. This is a much higher share of land than the 4% that is under permanent crop. Currently, less than 3% of total bio-energy production comes from the agriculture sector. Additionally, 10% of the overall biomass for bioenergy comes from the agriculture sector in the form of crop residues. 2  Estimates suggest that utilising the residues of major crops can generate up to 9.4 billion tonnes of biofuel, which could meet up to 14% of the world’s energy requirements [10]. This serves to highlight the potential crops have as a source of biofuel. If residues alone are predicted to be capable of generating such energy, then dedicating even more available land to crops for biofuel production could further reduce reliance on fossil fuels. This is where brownfield sites could be utilised. Growing biofuel crops on available brownfield sites could allow for an increase in biofuel production without the need for deforestation or a decrease in land dedicated to food production.

Brownfield sites 

Brownfield sites are contaminated areas of land that previously had industrial or commercial development on them. There are around 450,000-600,000 registered brownfield sites in the United states [11], 342,000 in Europe [3] [12] and over a million contaminated sites in China [13] [14]. Meaning there is likely to be over 2 million brownfield sites worldwide. It is hard to know how many hectares of brownfield land there are globally. However, the average size of brownfield sites in the UK was found to be 1.62 hectares [15]. Using these statistics, there could be over 3.2 million hectares of unused brownfield around the world.  These sites would need to be remediated before they are suitable for growing biofuel resources. Bioremediation (through the use of microbes, such as bacteria) or phytoremediation (through the use of plants) could be performed as a cost-effective and environmentally friendly way of decontaminating the sites and making them suitable for crop growth [16][17]. This offers an exciting opportunity for land utilisation.  One plant species that shows great potential for use as a biofuel crop is Miscanthus (Miscanthus x giganteus), a perennial grass with bamboo-like shoots [18]. Miscanthus grows best in regions of Africa and southern Asia, but it has the ability to be grown in tougher conditions due to high levels of cold tolerance [19]. This means it could be planted worldwide [20]. It is a fast-growing crop that requires little maintenance and has a high yield to energy ratio [21]. It also has the potential to be carbon-negative, with an annual net removal of 24.5 tonnes of atmospheric CO2 per hectare [22]. For these reasons, Miscanthus is considered to be the most promising and sustainable energy resource [23].  One hectare of land can grow 17.3 tonnes of this crop annually, which can produce 63MWh of energy [24]. Therefore, if the available brownfield land became dedicated to growing Miscanthus then 201,600,000 MWh (201.6 TWh) of energy could be produced each year. This could also result in the annual removal of 78.4 million tonnes of CO2 from the atmosphere. 

Global food waste

Food waste could be utilised alongside brownfield sites in order to generate energy. In 2011 the FAO estimated that one-third of all food production becomes food waste, equivalating to 1.3 billion tonnes of food waste per year [25]. More recent predictions based on these results now believe that this has risen to 1.9 billion tonnes of food waste. This in turn produces 2.5 billion tonnes of greenhouse gas emissions each year [26]. 900 million tonnes of food are wasted by households each year, meaning that 1 billion tonnes of waste occurs before it is even available to consumers [27]. The majority of food waste gets put into landfill sites, where it breaks down and releases greenhouse gases such as carbon dioxide and methane. This contributes considerably to landfill sites being one of the largest sources of methane pollution [28]. Therefore, food waste is driving climate change, when it could be collected and used for something great. 3  Turning food waste into biofuel is quite a straight forward process, and one that is cheaper than extracting and using fossil fuels [29]. The waste gets mixed and pulped into a liquid before being pasteurised. Microorganisms are then used to break down the food waste and this produces methane, carbon dioxide and ethanol. These products can be collected and used as biogas or liquid biofuel to generate energy [30][31]. This is also a very efficient process that achieves 92-97% conversion [30]. 1 tonne of food waste has an approximate energy potential of 300kWh [32]. Therefore, the 1.9 billion tonnes of wasted food could generate a potential 570,000,000,000 kWh (570 TWh) of clean energy, while also preventing these harmful gases going into the atmosphere. 


Nowadays, people are more conscious of climate change than ever before and keen to do their part. Although this proposed initiative alone would not solve the climate crisis, it would be a significant step in the right direction. Utilising food waste and brownfield sites has the potential to produce 771.6 TWh of energy each year. This would meet 0.5% of the world’s annual energy demand. Along with more wind farms, increased use of crop residues and greater numbers of clean energy power stations, the amount of fossil fuels being burnt each year could be significantly reduced. Furthermore, the carbon-negative potential of Miscanthus and the reduction of decaying food waste within landfill sites could help to reduce the amount of greenhouse gases in the atmosphere over the long-term. This would contribute to slowing down the rate of climate change.  This initiative would also involve the people that climate change is affecting. The efforts of everyday people to recycle food waste will contribute to reduced reliance on fossil fuels. This, in collaboration with the increased productivity of previously contaminated brownfield sites, presents a promising step towards a greener future. With this initiative, each of us will have our part to play and the future of the planet is placed into everybody’s hands.


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