Crop Residue Management through Stepwise Slow Pyrolysis and Chemical Recovery : A case study for India with techno-economic and environmental assessment of a decentralized biorefinery
Bhatnagar, Anubhuti (2022)
Tampere University
2022
Tekniikan ja luonnontieteiden tohtoriohjelma - Doctoral Programme in Engineering and Natural Sciences
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Väitöspäivä
2022-09-07
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-03-2553-4
https://urn.fi/URN:ISBN:978-952-03-2553-4
Tiivistelmä
Pyrolysis-based technologies are being evaluated as an alternative to the open burning of residues by converting them into chemicals, fuels, and energy. However, there’s a need to develop methods to quickly process the large quantities of residue generated annually. This dissertation presents a method to treat crop residues on farms using stepwise pyrolysis, and evaluate the potential environmental and economic benefits of such a method. Stepwise pyrolysis involved heating the biomass gradually to improve bio-oil quality and ensure ease of operation for treating crop residues in decentralized units on farms.
The first stage of this work was to evaluate the role of biomass composition and stepwise pyrolysis conditions like temperature and number of steps on bio-oil yield and quality. Bio-oil from the first step was rich in organic acids, anhydrosugars, and carbonyl compounds. While bio-oil from the second step was rich in unbranched phenolic compounds. The second stage of the work was to improve pyrolysis product yield and quality from rice straw, by blending with groundnut shells and wheat straw, and washing with water. Combined water-washing and mixing biomass samples improved the yield of levoglucosan, a high-value chemical, by 1.6-2.1 times compared to unwashed rice straw. The third stage was to use an energy-efficient crystallization technique to recover pure crystals of levoglucosan from bio-oil. The recovery rate was observed to be 24%. The fourth and final stage of the work was to evaluate the economic and environmental feasibility of a stepwise pyrolysis-based biorefinery using crop residues as feed and operating in Punjab (India), where up to 80% of residues are openly burned. It was calculated that setting up biorefineries in 10 districts with the highest open fire incidents would provide an annual saving of 3.5–9.4 Gg (Gigagram, 109 g) CO2eq emissions from avoided straw burning. The biochar application in soil may allow the sequestration of 19–20 Gg CO2eq and avoid 35–36 Gg CO2eq emissions annually in thermal power.
The major contribution of this work is providing experimental evidence for the usability of stepwise pyrolysis for treating crop residues and recovering multiple products like levoglucosan from bio-oil and high-quality biochar. It may be especially useful for setting up a decentralized unit in regions where these residues are otherwise openly burned due to prohibitive collection costs.
The first stage of this work was to evaluate the role of biomass composition and stepwise pyrolysis conditions like temperature and number of steps on bio-oil yield and quality. Bio-oil from the first step was rich in organic acids, anhydrosugars, and carbonyl compounds. While bio-oil from the second step was rich in unbranched phenolic compounds. The second stage of the work was to improve pyrolysis product yield and quality from rice straw, by blending with groundnut shells and wheat straw, and washing with water. Combined water-washing and mixing biomass samples improved the yield of levoglucosan, a high-value chemical, by 1.6-2.1 times compared to unwashed rice straw. The third stage was to use an energy-efficient crystallization technique to recover pure crystals of levoglucosan from bio-oil. The recovery rate was observed to be 24%. The fourth and final stage of the work was to evaluate the economic and environmental feasibility of a stepwise pyrolysis-based biorefinery using crop residues as feed and operating in Punjab (India), where up to 80% of residues are openly burned. It was calculated that setting up biorefineries in 10 districts with the highest open fire incidents would provide an annual saving of 3.5–9.4 Gg (Gigagram, 109 g) CO2eq emissions from avoided straw burning. The biochar application in soil may allow the sequestration of 19–20 Gg CO2eq and avoid 35–36 Gg CO2eq emissions annually in thermal power.
The major contribution of this work is providing experimental evidence for the usability of stepwise pyrolysis for treating crop residues and recovering multiple products like levoglucosan from bio-oil and high-quality biochar. It may be especially useful for setting up a decentralized unit in regions where these residues are otherwise openly burned due to prohibitive collection costs.
Kokoelmat
- Väitöskirjat [4926]