Environmental-economic assessment of the pressure swing adsorption biogas upgrading technology

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.