A comparison between various disposal options for wood is also conducted in ‘Greenhouse gas balances in
building construction: wood versus concrete from life-cycle and forest land-use perspectives’ (Börjesson &
Gustavsson, 2000). Although this study does not follow the LCA methodology, it includes three scenarios for
disposal of wood waste, i.e. incineration with energy recovery, 50% of the wood reused as building materials and
50% incinerated, and landfill. The results show that recycling is slightly preferable to incineration with
energy recovery regarding GHG emissions. Landfill is reported to be the worst option, incineration
being 60% better. A comparison of the performances of landfill with and without biogas collection is also
conducted. It reveals that the landfill benefits increase by 70% if there is biogas capture and recovery of energy.
However, the overall ranking between alternatives is not affected.
A case study was also conducted in Vienna by Adolf Merl (2007) to compare energy recovery, recycling as sawn
timber and particleboards and landfill regarding the impacts on climate change. This case study was conducted
using a combination of regional mass flow analysis and LCA methodology. The results obtained are in line with
the previous observations since landfill appears by far as the option with the most associated emissions while
recycling seems slightly preferable to incineration.
The DEFRA project that led to the report ‘Carbon Balances and Energy Impacts of the Management of UK Wastes’
(ERM, 2006) also evaluates greenhouse gas benefits and impacts associated with alternative management routes
for wood waste. Nevertheless, it should be noted that this study cannot be qualified as an LCA. The results
showed that incineration with energy recovery is more favourable than recycling for energy
demand but also for climate change. In addition, the study highlights that the extent of the recycling
benefits depend on the assumptions regarding the quality of the wood wastes that determines the
recycling route. The benefits from recycling high quality wood waste into timber products or firewood^4 were
compared with the benefits from recycling low quality wood waste into particleboard. The benefits turned out to
be much higher in the first case.
Lastly, WRAP recently published an LCA on a specific wood recycling technology, the Microrelease process, which
recovers wood fibres from medium-density fibreboard (MDF) waste using microwave technology (WRAP, 2009
(a)). The study assumes that the fibres produced through this technique are put back into the MDF
manufacturing process. This study includes a comparison between this type of recycling, incineration and landfill
disposal. The results highlight that disposal by landfill has the highest environmental impact for the ten
impact categories considered. Thanks to the avoided production of virgin fibre but also to the avoidance of
disposal of the MDF through conventional routes, recycling of MDF waste brings some significant environmental
benefits but nevertheless it is a complicated trade-off between recycling and incineration with energy
recovery. Indeed, the scenario for heat and power cogeneration has a marginally lower environmental impact in
most impact categories while in contrast, when considering only heat or only power generation, Microrelease
appears as a better option.
The overall conclusion therefore seems to be that wood incineration with energy recovery brings
more energy credit, especially if both heat and electricity are generated, while recycling appears
more advantageous when it comes to climate change potential. On the other hand, wood landfill is
to be avoided due to the associated methane emissions.
3.6.3 Comparison with the results from the previous report edition
In the previous edition of this review, the evaluation process resulted in the selection of only three studies.
Among these three studies, seven scenarios comparing incineration and landfill were identified. In all scenarios,
the incineration of wood waste was found to be preferable to landfill. No evaluation of recycling was included.
3.6.4 Data gaps/further research......................................................................................
First, there is a need for LCAs studies dedicated to the comparison of the alternative options for the management
of wood wastes. In addition, it should also be noted that the few studies dealing with wood waste management
that have been reviewed in this study focus on the climate change potential and energy consumption. The
analysis of a larger set of indicators would be required in order to be able to come up with reliable evidence of
the benefits of wood recycling.
(^4) We assume that it is the waste from the timber production that is converted into firewood but this is not clear in the study