Preserving sugarcane trash for year-round biogas production: effects of additives on ensiling properties and methane potential

Janke, L. and McCabe, B.K. and Hill, A. and Lee, S. and Harris, P. and Marchuk, S. and Baillie, C. (2019) Preserving sugarcane trash for year-round biogas production: effects of additives on ensiling properties and methane potential. In: 41st Annual Conference of the Australian Society of Sugar Cane Technologists (ASSCT 2019), 30 April - 3 May, 2019, Toowoomba, Australia.


Abstract

Sugarcane trash (SCT) composed of tops, and dry and green leaves represents the non-millable fractions of cane that is usually left to decay on the fields for soil protection after mechanized harvesting. The fractional recovery of this material for biogas production can potentially result in generation of renewable energy without negatively influencing soil quality, since digestate from the anaerobic digestion process can be used as a soil conditioner. However, as the length of the sugarcane harvesting season is around 6 months per year, strategies for biomass preservation that allow SCT to be used as a substrate throughout the entire year are required. Therefore, the present study aimed to optimize the ensiling of SCT using a commercial lactic acid bacterial (LAB) inoculant to promote lactic acid (LA) fermentation with the addition of molasses to increase the content of biodegradable sugars. The ensiling experiments were conducted in laboratory-scale silo-bags under anoxic conditions with the following additives applied to the sugarcane biomass: SCTctr (no additives); SCTmol (addition of molasses); SCTmol+lab (addition of molasses and lactic acid bacteria); and SCSctr (sugarcane stalks without additives). The experiment was run for 70 days and the following parameters were analyzed at days 0, 5, 15 and 70: total and volatile solids, total volatile fatty acids, LA, ammonium-nitrogen, pH and solubilized chemical oxygen demand (COD). Biochemical methane potential (BMP) tests were performed with fresh and ensiled material at day 70 to assess energy losses/gains due to ensiling. In general, the results showed a decrease in pH from 5.7-5.9 to 3.8-4.2 for all SCT treatments during the ensiling period. The rationale behind pH reduction lies in the increase in lactic acid concentration from 1.0-1.4 % DM (dry matter) up to 3.0 % DM in the SCTmol + lab treatment. SCSctr showed a marked increase in lactic acid (from zero to 3.7 % DM) resulting in the lowest observed pH of 3.7 among all treatments. The ensiling process increased methane yields by 17%, 39%, 17% and 79% for SCSctr, SCTctr, SCTmol and SCTmol+lab, respectively. Thus, ensiling of sugarcane is not only a suitable way for wet biomass preservation but also an effective method to improve the digestibility of sugarcane residues for biogas production.


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Item Type: Conference or Workshop Item (Commonwealth Reporting Category E) (Paper)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Agricultural Engineering (1 Aug 2018 -)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Agricultural Engineering (1 Aug 2018 -)
Date Deposited: 07 Aug 2020 05:10
Last Modified: 01 Oct 2020 00:28
Uncontrolled Keywords: Sugarcane stalks, pretreatment, lactic acid bacteria, molasses, anaerobic digestion, biochemical methane potential testing
Fields of Research (2008): 07 Agricultural and Veterinary Sciences > 0701 Agriculture, Land and Farm Management > 070108 Sustainable Agricultural Development
09 Engineering > 0904 Chemical Engineering > 090499 Chemical Engineering not elsewhere classified
Fields of Research (2020): 30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3002 Agriculture, land and farm management > 300210 Sustainable agricultural development
40 ENGINEERING > 4004 Chemical engineering > 400499 Chemical engineering not elsewhere classified
Socio-Economic Objectives (2008): B Economic Development > 85 Energy > 8505 Renewable Energy > 850501 Biofuel (Biomass) Energy
D Environment > 96 Environment > 9609 Land and Water Management > 960904 Farmland, Arable Cropland and Permanent Cropland Land Management
URI: http://eprints.usq.edu.au/id/eprint/36565

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