Greenhouse gas emissions reductions for the global paper system

The global paper life cycle contributes to 1% of annual global greenhouse gas (GHG) emissions. However, under a business as usual scenario, the cumulative emissions associated with paper will comprise 3% of the global... [ view full abstract ]

The global paper life cycle contributes to 1% of annual global greenhouse gas (GHG) emissions. However, under a business as usual scenario, the cumulative emissions associated with paper will comprise 3% of the global carbon budget required to stay below 2 degrees global warming to 2050. Emissions associated with the paper life cycle thus need to be cut with a factor 3. This study provides an insight into emission reduction options along the life cycle.

The study makes two major contributions to the literature. Firstly, it presents for the first time a detailed analysis of global greenhouse gas emissions from the paper life cycle including methane emissions from landfill. Earlier analyses were either at the national level or global level but highly aggregated. Many existent analyses also ignore the contribution of methane. This study provides credible insight about the contribution of paper consumption to global GHG emissions.

Secondly, it introduces three materials management scenarios: 1) business-as-usual, 2) increased mitigation efforts, and 3) maximum waste reuse. Scenario 2 represents a doubling of the business-as-usual trends in for example energy efficiency and recycling rates. Scenario 3 is based on a detailed analysis of the reuse potential of all major waste flows in the system (the reuse analysis was submitted for a poster presentation). This scenario serves to test whether closing all loops in the paper system is sufficient to meet carbon targets.

The model distinguishes emissions from forestry, pulping, papermaking, and waste management. It considers emissions from fossil fuel use, electricity use, landfill decomposition, and lime kiln operations. Paper consumption to 2050 is based on a forecast that appreciates the role of GDP per capita and GDP growth, the recent financial crisis, leapfrogging in media, and demand saturation. Energy intensity of production is projected using industrial learning curves.

Preliminary results suggest that a combination of scenarios 2 and 3 will be required to reduce emissions from the paper system at the same speed as the desired global reductions. Even at maximum waste reuse, some virgin inputs are still needed, and their processing remains energy intensive. In other words: the paper sector needs to reuse the wastes it generates and to increase mitigation efforts, for example through fast decarbonisation of its heat supply.

Under any scenario, fossil fuel and electricity consumption remain significant contributors to overall emissions. Chemical pulping mills can be energy self-sufficient but their market share decreases with increased recycling. Mechanical pulping mills can be supplied with external biomass but this competes with other uses such a timber production.  The key to greening the paper industry seems complete decarbonisation of the grid.

The results suggest that more profound changes in materials management should be explored. For example: the paper sector aims to use lignin wastes more efficiently through gasification instead of combustion but in the long term lignin might be used as a substitute for crude oil in the petrochemical industry. Another avenue is demand reduction. Such ideas deserve exploration and require widening of the system boundaries beyond the paper system.