The role of biomass in a time of energy transformation

Atlantic Canada, like the rest of the world, will be attempting to meet the twin challenges of climate change and energy security in a time of market volatility for at least the next 50 years. This will mean breaking our reliance on fossil fuels—no simple task, given that oil, natural gas, and coal meet about 80 percent of the world’s energy demand. Not surprisingly, these three energy sources, plus some derived from them, notably electricity, influence just about every aspect of our lives, from the food we eat to where we live. Like it or not, we will have to change.

There are only three actions that we can take. The first is reducing our energy requirements through conservation or adopting energy-efficient practices. Although energy reduction helps, it doesn’t necessarily break the reliance on fossil-fuels, only delaying the inevitable two remaining actions: replacing existing fossil-based energy sources and restricting any new demand to energy sources that are environmentally benign and have less exposure to the vagaries of world energy markets.

One such energy source that can meet these requirements is forest or woody biomass (simply referred to as “biomass” for the rest of this article). In fact, biomass can be seen as the ideal energy source because not only is it a solid fuel, it can be transformed into both liquid and gaseous fuels. Despite its benefits and flexibility, if biomass is going to be part of our energy future, we must extract as much energy as possible from every unit of biomass (for example, cord or tonne) consumed while ensuring future supplies of biomass.

Maximizing the energy available in a unit of biomass is more than just the combustion technique, it is equally important to consider how the energy from the combustion is used. Ensuring future biomass supplies will require having the necessary policies and programs in place to enforce sustainable forest management techniques, including active reforestation programs, nutrient monitoring and application, and proper harvesting techniques.

Earlier this year, Nova Scotia Power announced two biomass-related projects intended to help it meet the greenhouse gas emissions targets required by the province. The first of these was co-firing biomass with coal for the production of electricity, in which some of the coal required for electrical generation is replaced with biomass.

When biomass is co-fired with coal, the total greenhouse gas emissions for the amount of electricity generated is about the same as for burning coal alone. However, if the source of biomass is subject to sustainable forest management techniques, the biomass can be considered carbon neutral (that is, the amount of CO2 released from the biomass during combustion is equal to the amount of CO2 consumed during its growth). This allows electricity generators such as NSP to claim that co-fired biomass effectively emits no greenhouse gases, meaning that the net-CO2 per unit of electricity generated from co-firing is less than for coal.

Although co-firing with biomass from sustainably managed forests would lower NSP’s emissions, it cannot be said that burning biomass with coal will meet either of the requirements for our future energy needs. Our forests need nutrients, many of which can be obtained from biomass ash (that is, the material remaining after combustion). In fact, countries such as Sweden require that biomass ash be returned to the forest for this very reason. However, by co-firing biomass with coal, the ash becomes contaminated with the metals and other pollutants associated with coal, making the ash unsuitable for use in improving the nutrients of the forest.

NSP’s other biomass-related project is the planned purchase of biomass-generated electricity from Strait Bio-Gen. As with co-firing, NSP will claim that any electricity purchased will be carbon-neutral, improving NSP’s overall carbon intensity (that is, the amount of carbon in the form of carbon dioxide emitted compared with the volume of electricity generated).

Although the ash produced from biomass-generated electricity can be used to enhance the nutrient content of the forest, it does not necessarily mean that the energy content available in the biomass has been maximized. Generating electricity from biomass is a result of the energy in the biomass being released through combustion, which heats water in a boiler to create steam to spin a turbine connected to an electrical generator. The overall efficiency of this process is typically around 30 percent (30 percent of the energy in the biomass is used to produce electricity, while the remaining 70 percent is lost because of inefficiencies).

Wasting 70 percent of an energy source may have been acceptable to electricity suppliers when energy was plentiful and cheap, but it will be inexcusable in the twenty-first century. Perhaps the best example of the absurdity of producing electricity from biomass is to consider its possible use for space heating, the energy service with the second largest energy demand in Nova Scotia (transportation being the first).

By definition electric heating is 100 percent efficient, in that all electricity passing through a radiator is released to the environment as heat. Although electric heating may be 100 percent efficient, the generation of electricity is not; if the electricity was generated from biomass, less than 30 percent of the energy in the biomass was actually used for space heating.

Had the same amount of biomass been consumed in a biomass furnace in the building, the amount of energy obtained from the biomass for heating could be much higher. For example, some pellet furnaces have efficiencies approaching 85 percent, while some woodstoves have efficiencies of 80 percent. Given the importance of extracting as much energy as possible from the available supply of biomass, using electricity generated from biomass makes little sense if it is consumed in space heating.

This doesn’t mean that biomass shouldn’t be used to generate electricity rather that there are better ways of utilizing the biomass than simply combusting it for electricity. It is possible to generate electricity and capture some of the “waste” heat for space heating. This is an example of “combined heat and power”, a biomass generation facility that produces both heat and electricity; the heat is transmitted in insulated pipes (usually buried underground) to buildings throughout the community. The overall efficiency of the system (that is, the amount of biomass energy actually used) increases from 30 percent (electricity only) to 65 or 70 percent (about 25 percent for electricity and the other 40 to 45 percent for heating).

The world’s energy systems are in the process of undergoing a significant transformation because of climate change and the need for energy security. If biomass is to play a role in this transformation, it must be used as efficiently as possible and managed sustainably. In Nova Scotia, provincial government’s energy policies do not reflect this new reality.

Invited guest editorial for Atlantic Forest Review
Larry Hughes
30 September 2009