# Life Cycle Assessment on a Biorefinery Approach to Pyrosis Oil for Wood Modification Treatment
## 4 Discussion  
For the production of pyrolysis oil two feedstocks were compared, forestry residues and maize digestate. The most striking result in this comparison was a higher impact on damage to human health and a significant increase in resource scarcity for maize digestate. The large change in impact could be explained by a couple of aspects of the processes. First, the pyrolysis oil yield on maize digestate was lower. Second, maize digestate contained more ash than forestry residues (30% for maize digestate vs. 2.0% for forestry residues). Third, the energetic value of the pyrolysis oil from maize digestate was lower (13.1 MJ/kg) than for pyrolysis oil from forestry residues (16.0 MJ/kg). The lower yield in both material and energetic aspect resulted in a higher amount of maize digestate required for the production of the same energetic value in pyrolysis oil. This resulted in more transport of feedstock. Together with the higher requirements of ash treatments, these factors resulted in higher environmental impacts. Further, regarding the comparison of the use of pyrolytic sugars compared with the fossil-based creosotes, unsurprisingly, the bio-based wood modification had a lower impact on resource scarcity than using creosotes. Moreover, due to the toxic nature of creosotes, the impact on human health was significantly larger for the use of creosotes than when the pyrolytic sugars were used. The small difference in damage to ecosystems could be explained by the fact that this impact factor was dominated by the impact of the land use required to fabricate the wooden pole itself. The determined environmental impact of pyrolysis oil could be brought into context of other studies and life cycle assessments. However, the calculations in these studies were based on models rather than real practice. Moreover, the feedstock was often different, and the geographical boundaries were often outside of Europe. Since most LCAs focus on global warming, the greenhouse gas (GHG) emission of pyrolysis oil from this study was compared to the GHG emissions from other studies (Figure 4). In Figure 4, the results of this LCA were compared to two other published LCAs. In the work of [PERSON] et al., the impact of biofuel from corn from pyrolysis oil, using corn stover in the US as feedstock is calculated at 28.83 g CO\({}_{2}\) eq per MJ biofuel, which translates to 353 g CO\({}_{2}\) eq/tonne pyrolysis oil [16]. This is similar to our result of 376 g CO\({}_{2}\) eq for 1 tonne of pyrolysis oil from forestry residues. A second study shows an impact of 30 g CO\({}_{2}\) eq per MJ biofuel based on pyrolysis oil from horse manure. In this study, a tail gas reactive pyrolysis is modeled on horse manure to produce aviation fuel and phenol. This would result in a GHG emission of 11 g CO\({}_{2}\) eq per tonne pyrolysis oil [17]. This impact is significantly lower since no impacts are considered from the horse manure \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Amount Sent to Landfill**} & **Difference in Impact to** & **Difference in Impact to** & **Difference in Impact Resource** \\  & **Ecosystems (Species \(\times\) Year)** & **Human Health (DALY 1)** & **Sacacity (USD 2013 2)** \\ \hline
1\% & \(0.52\times 10^{-7}\) & \(4.71\times 10^{-5}\) & 0.40 \\ \hline
50\% & \(0.42\times 10^{-7}\) & \(4.34\times 10^{-5}\) & 0.35 \\ \hline
99\% & \(0.32\times 10^{-7}\) & \(3.97\times 10^{-5}\) & 0.29 \\ \hline \hline \end{tabular} Differences were calculated by subtracting the impact of 1 m\({}^{3}\)a wooden poles treated with pyrolytic sugars from 1 m\({}^{3}\)a wooden poles treated with creosotes. 1 DALY = disability adjusted life years, and 2 USD2013 is the value of the US dollar in 2013.  
\end{table} 
Table 1: Impact of end of life scenario on the endpoint scores of 1 m\({}^{3}\)a pyrolytic sugar treated wooden poles. and the phenol replaces petroleum-based phenol.