Using a Life Cycle Assessment (LCA) has many benefits. However, it’s important to keep in mind that the results of a LCA are determined by the choices the researcher makes. These choices affect indicators, functional unit, allocation and system boundaries. Especially in the circular economy, with its innovations involving recycling, reuse and circular design, LCAs can be quite complex.
An interesting example of how we need to treat Life Cycle Assessment results very carefully, is the comparison of the life cycles of paper (or board) products produced from virgin and recycled fibres.
An “odd” conclusion
Around 2009 there was an interesting discussion in the Netherlands about a report that compared the environmental impact of different packaging materials. In this report, the CO2 emission over the life cycle of virgin based paper products appeared to be lower than those of recycled fibre based products. To many, this result seemed rather counter-intuitive and asked for further research.
In order to determine whether or not virgin fibre based products had a lower environmental impact, I performed a study together with Jobien Laurijssen. We created an Excel model to map the mass flows and energy use of the main production processes of different paper production routes in detail.
CO2 vs energy footprint
This study demonstrated the huge benefits in terms of energy use over the total life cycle, by using recovered fibre instead of virgin fibres. The main reason was that the energy required to convert wood into pulp for papermaking, is very large, whereas turning recovered paper into pulp on the other hand requires very little energy (note that the quality of the fibres of virgin pulp differs significantly from recovered paper pulp).
What is interesting from a CO2 emission perspective, is that when wood is converted into pulp using chemical pulping, the process, although incredibly energy intensive, does not emit much CO2. The reason for this is that it uses mostly bio-energy to fuel its energy needs. Wood consists partly of cellulose, hemi-cellulose and lignin. In chemical pulping, only the cellulose is extracted and the rest is burned for energy recovery. This way, you emit virtually no net CO2 emissions because you use bio-fuel. This means that for every tree, you are only using half its mass to produce paper, while using the other half to produce bio-energy.
At the end of the life-cycle, the used paper can be either recycled or incinerated (let’s assume the paper is not landfilled). When assuming that the paper is incinerated for energy recovery, you can argue that this saves CO2 emissions by saving fossil fuels. When recycling the paper on the other hand, one cannot allocate such CO2 savings due to energy recovery. This also reduces the CO2 emissions of virgin fibre paper products in comparison to using recovered fibres.
As you can see, although intuitively it may seem clear that recycling of paper is beneficial to the environment over using virgin fibres, when you compare the CO2 footprints the results may show a different outcome, depending on the system boundaries that you take into account. From an energy perspective, there is not much discussion, since recycling of paper saves you that highly energy intensive process of turning wood into pulp. But when it comes down to CO2 emissions, the LCA interpretation becomes much more complex.
Expand the system boundaries
So how can we solve this dilemma? Our research shows that a good solution is to expand the boundaries of the LCA system, and include wood as a resource that has to be used in equal amounts in both the production of paper and board from virgin fibres and recycled fibres. If you assume the “saved” wood due to recycling of recovered paper, for direct energy conversion, then the research of Jobien Laurijssen and me clearly shows that using recovered fibres has a much lower environmental impact than using virgin fibres.
Thomas Dietz (LCA) firstname.lastname@example.org
Siem Haffmans (LCA / sustainable packaging) email@example.com