Carbon Dioxide (CO2) is a gas emitted by power stations that use coal, gas, oil or biomass as fuel. Once in the atmosphere the gas acts as a blanket to keep the earth warm. Plants use carbon dioxide to grow so they remove some gas from the atmosphere. If more CO2 is emitted than plants can absorb the concentration of the gas in the atmosphere goes up and this is one of the causes of global warming.
For all of human history up until about 200 years ago, the atmosphere contained around 275 parts per million (ppm) of CO2. The industrial revolution has since then led to ever increasing amounts of CO2 emissions from power generation and the atmosphere now contains around 390ppm of the gas.
In 2007 the UN Intergovernmental Panel on Climate Change (IPCC) predicted that the inhabitants of developed countries such as the UK, need to reduce our emissions by 80-95% in order to stabilize atmospheric CO2 at 450ppm. If this can be achieved, the scientists predict we have a 50/50 chance of limiting global warming to 2 degrees. However, no-one is sure whether a 2 degree rise will be OK, catastrophic or merely difficult to adapt to.
By 2008 most scientists were of the opinion that the worst case IPCC scenario trajectories, or even worse are being realized and that a 450ppm concentration of CO2 +/- 100ppm could lead to ice free polar regions and a whopping 220 feet rise in sea level.
So, whilst the UN has opted to try and stabilize atmospheric CO2 at 450ppm, many people would like to aim lower.
Hence everything we do at 350 Energy is aimed at helping to achieve a 350ppm target for atmospheric CO2.
If you’d like to know more, please give us a call!
Renewable Energy and the 350 target
At 350 Energy we describe the projects we advise on and develop as being “low carbon” rather than carbon free.
The fuel supply used in renewable energy systems, such as solar PV, solar thermal and wind is completely carbon free but we have to consider the energy and emissions that go into building the equipment we need to use together with any emissions associated with transporting those goods around the world.
We therefore need to do some sums before we can tell whether a renewable energy system is making a positive contribution to the 350 target. Whether a project is worthwhile therefore depends on three things:
- The energy and other resources used to make and install the renewable energy system
- The energy it will generate over its lifetime, which in turn may depend on the amount of wind or solar energy available at the project location
- The nature of the electricity generation and its emissions that is being displaced by installation of the project.
Calculating this balance, often called a carbon footprint or carbon pay-back, has been undertaken by numerous researchers for many different technologies.
For solar PV, the variations described above leave researchers producing different carbon payback periods, but they all tend to range between 2 and 5 years. Given that a PV system should last 25 years or more, we can be comfortable that PV makes a worthwhile contribution to the 350ppm objective.
Biomass fuelled renewable energy systems are slightly more complex. This is because burning wood emits carbon dioxide, so to be low carbon the biomass burned must be re-planted and re-grown in order to balance the emissions from burning. Growing biomass often requires fertiliser, which usually comes from a fossil fuel source. Also biomass crops may need to be transported long distances from the forests to the power stations so this too consumes energy and creates emissions. For biomass projects we therefore have to ensure that the project has worthwhile benefits in terms of CO2 balance. Studies for some industrial scale biomass projects have indicated that their carbon balance is 70% better than that of fossil fuels and at 350 Energy we think this level of benefit is worthwhile so long as the biomass supply chain is operating sustainably.