Energy is required in various forms to turn a tree into paper. In some cases, both fossil fuels (petrol, diesel, gas, oil and coal) and renewable fuels (biomass and black liquor) are used to power these processes. Black liquor – a by-product from digesting pulpwood chips in the chemical pulping process – is a mixture of spent cooking chemicals and dissolved wood solids. This is concentrated during the chemical recovery process to yield a fuel which is rich in organic material. The black liquor – regarded as renewable and carbon neutral – is then used to produce energy. Some mills generate all or some of their own electricity by way of condensing power generation and co-generation.
Energy is used for direct process heating and the generation of steam which is the main heating medium in the papermaking process. Steam is also used for energy-efficient electricity generation.
Condensing is the term used for the electricity generation process typically employed by conventional coal-fired power stations. As the industry uses a combination of fossil-based and renewable fuels, the energy produced has a lower carbon impact than power production relying exclusively on coal. Co-generation refers to the generation of electricity from steam created as a by-product of the papermaking process.
Co-generation is the industry’s main method of generating electricity. Steam produced by boilers and furnaces is typically at a temperature and pressure which is too high for use in the pulp and papermaking process. This high pressure steam is passed through a back-pressure turbine where it expands, thereby spinning within the turbine which generates electricity.
Co-generation offers a number of advantages over condensing power generation:
- A greater portion of the input energy from the base fuel can be used in the production process;
- GHG emissions attributed to generated electricity are significantly
- Water consumption attributed to electricity generation is almost negligible.
Electricity derived through co-generation (using coal only) has been approximated to have less than half the GHG impact of electricity imported from the national grid (mostly from coal-fired sources). Co-generated electricity derived from gas (and not only coal) has an estimated smaller carbon impact of approximately 25% of the impact of electricity imported from the national grid.
Since there is very little water loss attributable to electricity generated via co-generation, this further implies that this method of power generation is a suitable option, within the water scarce context of South Africa. It is important to note however, that although the pulp and papermaking industry does generate a significant portion of its own electricity, it presently remains reliant on the national grid for the balance of its power needs.
Opportunities for co-generation and the sale of power back into the national electricity grid are being actively pursued by PAMSA members.
Forestry operations in South Africa are currently engaged in developing a bio-energy project that will clarify our approach to managing the interest shown by potential investors and impacts that the removal of bio-energy may have on forest residue.
The industry recognises the potential to further reduce GHG emissions through direct and indirect energy and carbon efficient practices, thereby contributing to reducing the national GHG footprint.
- Direct reduction in process energy and electricity use i.e. using less energy and electricity in the production of pulp and paper products will help the industry to reduce its reliance on fossil fuels, as well as fossil fuel-derived electricity;
- Maximising the use of available renewable fuels, which are carbon neutral, allows the industry to use less fossil fuel for its energy requirements;
- Maximising the level of co-generation reduces the reliance of the industry on the national power grid, and simultaneously reduces the carbon impact of the industry that is associated with electricity consumption, thereby reducing electricity imported from the national grid; and
- Seeking opportunities to move to cleaner burning fuels, such as gas. Gas is a relatively clean-burning fossil fuel with a lower carbon impact per unit of energy when compared with coal. While some operations use gas, this can be limited, by availability and distribution constraints. Where possible, however, the industry will continue to pursue opportunities for increased gas utilisation and reduced reliance on coal supplies.
Indirect opportunities for energy and carbon efficient practice:
- Using more recycled fibre: the amount of energy involved in making a piece of paper from virgin wood fibre is higher than that required to convert waste paper into new paper products. Increasing the amount of recycled paper used in paper manufacture will result in a decrease in the amount of fossil-based energy required, and in turn reduce the industry’s carbon impact. While it is not possible to produce all grades of paper with recycled fibre, the industry seeks to maximise its use of recycled fibre where possible; and
- Promoting the concept of ‘reduce, reuse, recycle’: the industry encourages the reuse and recycling of its products, as well as the minimisation of waste.