Is bioenergy ever truly green? It depends on 5 key questions

By Jessica Allen, University of Newcastle

Plans to revive an old coal-fired power station using bioenergy are being considered in the Hunter region of New South Wales. Similar plans for the station have previously not gone ahead. As we grapple with decarbonisation, bioenergy (energy derived from harvested trees and other plants) is often put on the table as an environmentally friendly alternative to fossil fuels.

But is it environmentally sound? The annoying answer is: it depends.

Trees and other plants soak up carbon from the atmosphere and store it as biomass. When they are burnt for electricity production the same carbon is released. This would suggest bioenergy is “carbon-neutral”.

But it’s not that simple. Many things can change the environmental credentials of a bioenergy project. Every project is unique and must be considered independently.

So let’s break down the five key questions we should ask about every bioenergy project.

1. What is the source of the biomass?

The bewildering array of plants on our planet means a huge amount of biomass “feedstock” is available. So what should we use?

First, we do not want to be cutting down native forests. Even using native forestry “residues” (by-products like bark and ends of trees that can’t be directly used) is problematic. The residues are made regardless of the bioenergy project, but tethering a power station to the native forestry industry, and creating a reliance on it continuing, is contentious. Some states have already flagged the end of native logging.

Fast-growing biomass species such as mallee could instead be harvested as purpose-grown energy “crops”. This can seem like an attractive option, but the sheer amount of land needed for energy crops on any reasonable scale can be prohibitive.

Agricultural residues and “waste” biomass, such as organic material sent to landfill (from household bins, for example), are also readily available. The Australian Bioenergy Roadmap shows large amounts of potentially usable waste biomass nationally.

In most cases waste biomass would otherwise go into landfill, be burnt in an open field or be left to decompose without emission controls.

Read Full Story https://theconversation.com/is-bioenergy-ever-truly-green-it-depends-on-5-key-questions-228202