Comparison of solid-state anaerobic digestion and composting of yard trimmings with effluent from liquid anaerobic digestion

Published Date

October 2014, Vol.169:439–446, doi:10.1016/j.biortech.2014.07.007

Title 

Comparison of solid-state anaerobic digestion and composting of yard trimmings with effluent from liquid anaerobic digestion

• Author 

• Long Lin ^a,b
• Liangcheng Yang ^a
• Fuqing Xu ^a,b
• Frederick C. Michel Jr. ^a
• Yebo Li ^a,,

• aDepartment of Food, Agricultural and Biological Engineering, The Ohio State University, Ohio Agricultural Research and Development Center, 1680 Madison Ave., Wooster, OH 44691, USA
• bEnvironmental Science Graduate Program, The Ohio State University, 3138A Smith Lab, 174 West 18th, Columbus, OH 43210, USA

Received 13 May 2014. Revised 30 June 2014. Accepted 1 July 2014. Available online 8 July 2014.

Highlights

• •
  Solid-state anaerobic digestion (SS-AD) and composting were compared.
• •
  High total solids content negatively affected performance of SS-AD and composting.
• •
  The preferred feedstock/effluent ratio for SS-AD was 4–6.
• •
  The total carbon loss during composting was up to 50% greater than that in SS-AD.
• •
  Both SS-AD and composting generated nutrient-rich (N, P, K) end products.

Abstract

Solid-state anaerobic digestion (SS-AD) and composting of yard trimmings with effluent from liquid AD were compared under thermophilic condition. Total solids (TS) contents of 22%, 25%, and 30% were studied for SS-AD, and 35%, 45%, and 55% for composting. Feedstock/effluent (F/E) ratios of 2, 3, 4, 5, and 6 were tested. In composting, the greatest carbon loss was obtained at 35% TS, which was 2–3 times of that at 55% TS and was up to 50% higher than that in SS-AD. In SS-AD, over half of the degraded carbon was converted to methane with the greatest methane yield of 121 L/kg VS_feedstock. Methane production from SS-AD was low at F/E ratios of 2 and 3, likely due to the inhibitory effect of high concentrations of ammonia nitrogen (up to 5.6 g/kg). The N–P–K values were similar for SS-AD digestate and compost with different dominant nitrogen forms.

Graphical abstract

Solid-state anaerobic digestion (SS-AD) and composting of yard trimmings with effluent from liquid anaerobic digestion were conducted at TS content of 22–30% and 35–55%, respectively. Carbon loss was compared at feedstock to effluent ratio ranged from 4 to 6. The greatest total carbon loss was observed at 35% TS in composting, which was about 50% higher than that in SS-AD; while, using SS-AD, more than half of the degraded carbon was converted to methane as a renewable energy carrier.

Keywords

• Solid-state anaerobic digestion
• Composting
• Thermophilic
• Biogas
• Carbon loss

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• ⁎ 
  Corresponding author. Tel.: +1 330 263 3855.

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