Heat Recovery from Composting: A Comprehensive Review of System Design, Recovery Rate, and Utilization

Abstract

It has long been recognized that composting yields a large quantity of thermal energy, which is normally lost to the surrounding environment as heat. Efforts to recover this heat using compost heat recovery systems (CHRSs) have been sporadic. Literature on the subject is also disjointed. To summarize the research that has been conducted, the authors performed an extensive literature review, covering publications in scientific journals, trade magazines, books, theses, and published reports. A focus on CHRS design and heat recovery rates is presented. The review covers 45 CHRSs in 16 different countries, ranging from simple hotbeds used in China 2000 years ago, to advanced super-thermal conductor heat pipe systems in 2016. Heat recovery rates varied significantly, with no predictable trend among the 45 systems. Recovery rates averaged 1895 kJ/hr (1159 kJ/kg DM) for lab-scale systems, 20,035 kJ/hr (4302 kJ/kg DM) for pilot-scale systems, and 204,907 kJ/hr (7084 kJ/ kg DM) for commercial systems.

Temperature measurement and performance assessment of the experimental composting bioreactor

“…Comparing results published in [11], where lab-scale reactors reached heat recovery rate 1895 kJ/h = 0.526 kW and pilot-scale reactors reached 20035 kJ/h = 5.565 kW, our composting system with top output of 4964 kJ/h = 1.379 kW belongs to weakly performing pilot-scale experimental bioreactors.…”

“…Recently, all systems using heat from composting processes have been united under term "Compost Heat Recovery Systems" (CHRSs), cf. [11,12].…”

Condenser-Type Heat Exchanger for Compost Heat Recovery Systems

“…The environment with the highest temperatures is created in the thermophilic phase that occurs immediately after initial heat-up provided that suitable compost mixture [1], its physical and chemical parameters, composting principles [2] as well as proper composting facility construction [3] and management [4] were respected. Compost Heat Recovery Systems (CHRSs) [5] are being reviewed [6], investigated and modeled [7] as well as developed in order to utilize the heat produced by bacterial metabolism. This biologically produced heat can be considered as low-temperature heat source [8] with the potential of becoming another method for sustainable energy [9] production from biomass [10] and a novel waste management strategy [11].…”

Mitigating Global Warming and Climate Change with Design of Super Efficient Greenhouse

“…[13] A large quantity of thermal energy is produced by composting but unfortunately, it is not used and it is lost in the surrounding environment as heat. [14] Recovery of different compost heat recovery systems was reviewed by Smith at al. (2016) who came to the conclusion that recovery rates averaged from 1895kJ/hr (1159kJ/kg DM) for lab scale systems to 204907kJ/hr (7084 kJ/kg DM) for commercial ones.…”

“…(2016) who came to the conclusion that recovery rates averaged from 1895kJ/hr (1159kJ/kg DM) for lab scale systems to 204907kJ/hr (7084 kJ/kg DM) for commercial ones. [14] Compostpower.org (2017) estimated that you can get 30000kJ/hr from 30m3 of shredded bark mulch composting mound. [12] Sanford (2011) reports that 25% of heating needs can be offset by active solar or subterranean heating.…”