Environmental-Economic Assessment of the Pressure Swing Adsorption Biogas Upgrading Technology

Abstract

A large-scale biogas upgrading plant using the CarboTech® technology with a treatment capacity of 1333 Nm3 biogas per hour was analyzed. Our scope of evaluation encompasses all technology steps that are necessary for upgrading biogas, i.e., both pretreatment and biogas upgrade. A cradle-to-gate life-cycle and life-cycle cost assessment (LCA and LCCA) methodology was used with the functional unit (FU) of 1 Nm3 of biogas upgraded in order to ease comparison with other biogas upgrading technologies. The calculation was made using the GaBi8 LCA software and databases of GaBi Professional, Construction materials, Food&Feed, and the ecoinvent3. We applied the CML characterization model with all its mid-point indicators. The mid-point indicators of the CML characterization model were aggregated after normalization by the CML2001 - Jan.2016 normalization factors. The normalized environmental impact was 541.74·10−15/Nm3 raw biogas. The highest environmental impacts were the marine aquatic ecotoxicity potential (15.705 kg dichlorobenzene-equiv./Nm3 raw biogas), the abiotic depletion potential (1.037 MJ/Nm3 raw biogas), and global warming potential (0.113 kg CO2-equiv./Nm3 raw biogas). The unit production cost of the PSA technology was 0.05-0.063 €/Nm3 raw biogas. The most considerable source of expenses was the operational cost from which 77% was spent on electricity. The initial investment, personal costs, and the reinvestment amounted to only 34% of the total costs for the whole life cycle. Strategies to lower the environmental burden of the PSA technology are to use green electricity and to optimize the size of the plant in order to reduce unnecessary material flows of building material and their indirect energy use. This can also lower investment expenditures while automatization and remote control may spare personnel costs.

Sustainability and Future Trajectories: How is Prospectivity Integrated into Life Cycle Sustainability Assessment?

“…First, all 23 articles were classified according to their research field in order to limit the analysis to the field of energy. Thus, 14 articles with reference to the energy sector could be identified, of which the authors focused on the prospective LCSA of propulsion systems for vehicles in 8 [11][12][13][14][15][16][17][18] and on fuels/energy carriers in 2 articles [19,20]. 4 studies dealt with the assessment of energy systems, 3 of which refer to countries like Spain or UK [21][22][23][24].…”

“…Stamford & Azapagic 2014 extrapolated injury rates to the future based on historical trends ( [24] p. 202). Moreover, we observed that some of the authors (5 articles) came up with own assumptions without citing sources or methods [11,14,17,18,20]. For instance, Onat et al considered two battery charging scenarios related to the electricity mix in their studies; in scenario 1 the electricity mix was based on the existing electricity infrastructure, in scenario 2 on solar power [17,18].…”

“…[12,19]). For instance, Kohlheb et al stated that "since electricity is an important source of emissions, we scrutinized how much difference a change in electricity mix can produce" [20] p.7. Furthermore, by considering future changes, most of the authors aimed to provide ex-ante decision support to various stakeholders (esp.…”

“…In 12 of the 14 articles, impacts related to all three sustainability dimensions were prospectively assessed. Only the authors Kohlheb et al [20] and Wang et al [12] have taken impacts just related to the ecological and economic dimension into account. Regarding the type of prospective data, we found that most of the authors (10 articles) changed the "electricity or fuel mix" over time, which had again an effect on the impacts within the different dimensions (e.g.…”

Biogas upgrading, economy and utilization: a review

“…Among all the parameters affecting the overall energy efficiency of the complete biogas upgrading process, the loss of CH 4 is the most significant. The pressure swing adsorption process has a slightly lower energy consumption than water scrubbing (WS) but consumes much more energy than the chemical adsorption process (Kohlheb et al 2020). The energy consumption required by the chemical adsorption process is about 15% less than the water scrubbing process (Vilardi et al 2020).…”