Report: new research is looking at how biogas can be produced to heat our homes from such biodegradable waste or material as maize, seaweed, fruit and vegetables

If you eat an apple, a banana or an orange, the energy you receive from those foods keeps you warm so could that same energy be used to heat your home? Our bodies are so well designed that we extract what we need from food to provide us with the energy we need, but can we mimic this to form Bio-energy? The answer is yes.

As engineers, we look at the problems we face in today’s world and come up with solutions to overcome such issues. One issue is the amount of waste material that ends up on landfill - how can we reuse this? Another is the treatment of waste-water - can we re-use this liquid? Finally, are there alternative methods for heating our homes or fuelling our cars?

Take that apple as an example. From the biological point of view, we chew ("mastication") the apple and swallow, leaving it up to the six major functions of the digestive system to achieve the goal of providing energy and nutrients to our bodies.

As engineers, we look at the problems we face in today’s world and come up with solutions to overcome such issues

From a mechanical engineering view-point, we can simulate this by what we refer to as "pre-treatment", something like using a blender to chop up the apple therefore mimicking the chewing process, and then we can collect the apple pieces into containers.

Now, we need to simulate the stomach. The stomach contains hydrochloric acid and digestive enzymes that continue the digestion of food that began in the mouth. Therefore we need to control pH and add in some enzymes. This is where our waste water or "sludge" comes into play. Adding certain portions of waste water to the reduced apple begins what we refer to as the "treatment" process.

However, we need to control the temperature (like body temperature) and we need to mimic the muscular action whereby the stomach muscles contract periodically, churning food to enhance digestion. Therefore our treatment involves the control of temperature and mixing of the material. 

Over a period of time, gasses are given off during the process and, when collected, they form what we call biogas/renewable energy. The full process described above is referred to as Anaerobic digestion. Biogas typically refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen.

Biogas can be derived from biodegradable waste or material (also known as biomass) such as fruit, vegetables, leaves, grass, weeds, leftover food scraps. This includes anything produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste.

Within our homes, shops, providers, we generate huge amounts of waste, particularly when it comes to fruits, vegetables, crops and so on. All of this waste could be converted into biogas to produce primarily methane (CH4) and carbon dioxide (CO2), which could heat the glasshouses which produce the fruit/vegetables, heat our homes, or fuel our cars etc. 

Production and use of biogas

The waste left over from this process can be used as fertilizer in our fields and glasshouses or have other re-forming functions. Any excess biogas can be supplied to the gas grid or used to produce electricity or biomethane. In doing this, we would reduce or eliminate our reliance on sending such waste to landfill and the effects large amounts of gasses been produced contributing to the greenhouse effect. So, yes the waste from your lunch, breakfast, dinner could heat your home!

In Dublin City University within the School of Mechanical and Manufacturing Engineering, we have been researching ways to produce biogas from products such as maize, seaweed, fruit and vegetables. While this all seems simple, the complex "mimicking" of the ideal mixtures of organic waste and sludge, optimal pre-treatment and treatment processes for individual substrates (e.g. apple) and mixtures of substrates (which is more realistic of waste material) is a challenge. However, it is one we intend to solve, so our industries can limit their waste and our homes/farms may look more like the following in the future.

The views expressed here are those of the author and do not represent or reflect the views of RTÉ