Can renewable energy sources power the world?
Can renewable energy sources power the world?

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course

Can renewable energy sources power the world?

8 Energy balance of bioenergy

The fuel energy ratio (FER) is the ratio of useful energy in the fuel compared to the total amount of fossil fuel used in producing that fuel, including that used to construct equipment. Where the ratio is less than one, more energy is used to produce the fuel than is available from that fuel.

Woody energy crops perform well, with FERs between 10:1 and 20:1 on a heat output basis, but biodiesel may achieve only 3:1. Ethanol from grain may barely break even at just over 1:1 in the worst case, though there is little consistency among estimates (Davies et al., 2009).

Table 4 The range of fuel energy ratios for selected bioenergy systems reported in the literature to 2016

Fuel energy ratioLowestHighest
Lignocellulosic alcohol (generalized)0.751.24
Switchgrass (combustion)0.444.43
Corn (alcohol)0.91.14
Miscanthus (rhizome to pellet combustion)1.779.23
Only one set of data for miscanthus systems was available.
Source: (Scurlock et al., 2018) (derived from and (Hastings et al., 2013))

Energy ratios can be improved by good design of the production and processing systems to ensure that no energy is wasted. Co-products, such as straw or bagasse, associated with biofuels can also be used to replace fossil fuels in supplying heat for the processes involved.

How much does bioenergy cost? You’ll look at this next.

RENBOC_1

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to university level study, find out more about the types of qualifications we offer, including our entry level Access courses and Certificates.

Not ready for University study then browse over 900 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus