Terpenes in biogas plant digesting biowaste from circular economy perspective : case: Ämmässuo biogas plant
Moussa, Karam (2024)
Diplomityö
2024
School of Energy Systems, Ympäristötekniikka
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe202401183222
https://urn.fi/URN:NBN:fi-fe202401183222
Tiivistelmä
This thesis is done as a commission of Helsinki region’s environmental services (HSY). The main aim is to find possible solutions for current and future terpenes removal and recovery from the biogas stream of the Ämmässuo biogas plant (ÄBP) to move towards resource efficiency by designing out terpenes as waste through industrial symbiosis.
The main findings show that the average annual concentration of terpenes between 2018-2023, particularly p-cymene and limonene, was 1 900 mg/Nm3 and represented on average 88% and 94.7% of all VOCs in biogas streams and processed water, respectively. P-cymene was the dominant component in biogas starting from 2019, with shares reaching up to 77%. Accordingly, out of 8 t of annually produced terpenes, 49,6 % of terpenes volume was transferred for disposal, and 51,4 % was combusted, generating energy of 49 MWh and revenue of 2,2 k €. The economic assessment for terpenes shows that introducing this waste as a renewable feedstock could increase the total terpenes revenue to 6,1 k €. The study also shows that as the biogas production capacity reaches 975 Nm3/h in 2030, the water scrubber will increase terpenes recovery to 80 %, total terpenes revenue to 13,5 k €, and total annual profit to 24,2 k €.
The current water scrubber (WS) and chemical scrubber (CS) prove to be unstable and unreliable in handling the high content of terpenes in the Ämmässuo biogas stream, and they raise uncertainty on efficiently preventing terpenes slips to biomethane. However, based on the preliminary quotations, correspondence, and results, the most recommended option for removing and recovering terpenes is redesigning the refrigeration stage by introducing pressure to enhance terpenes condensation by focusing the dewpoint on the most dominant terpenes. This procedure could help protect downstream machinery, provide quality products, and separate terpenes as potential renewable feedstock.
The main findings show that the average annual concentration of terpenes between 2018-2023, particularly p-cymene and limonene, was 1 900 mg/Nm3 and represented on average 88% and 94.7% of all VOCs in biogas streams and processed water, respectively. P-cymene was the dominant component in biogas starting from 2019, with shares reaching up to 77%. Accordingly, out of 8 t of annually produced terpenes, 49,6 % of terpenes volume was transferred for disposal, and 51,4 % was combusted, generating energy of 49 MWh and revenue of 2,2 k €. The economic assessment for terpenes shows that introducing this waste as a renewable feedstock could increase the total terpenes revenue to 6,1 k €. The study also shows that as the biogas production capacity reaches 975 Nm3/h in 2030, the water scrubber will increase terpenes recovery to 80 %, total terpenes revenue to 13,5 k €, and total annual profit to 24,2 k €.
The current water scrubber (WS) and chemical scrubber (CS) prove to be unstable and unreliable in handling the high content of terpenes in the Ämmässuo biogas stream, and they raise uncertainty on efficiently preventing terpenes slips to biomethane. However, based on the preliminary quotations, correspondence, and results, the most recommended option for removing and recovering terpenes is redesigning the refrigeration stage by introducing pressure to enhance terpenes condensation by focusing the dewpoint on the most dominant terpenes. This procedure could help protect downstream machinery, provide quality products, and separate terpenes as potential renewable feedstock.