Characterization of solid fuel chars recovered from microwave hydrothermal carbonization of human biowaste

Abstract

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT Highlights-Microwave hydrothermal carbonization can convert human biowaste to solid fuel chars -Physicochemical, structural, energetic and combustion properties of chars are enhanced -Higher heating value (HHV) of chars recovered increased by up to 41.5%-HHV of chars -up to 25.6MJ/kg -is greater than that of low-ranking coals/fuels -Processing human biowaste into solid fuel is promising for energy applications M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT KeywordsFaecal biomass, microwave, hydrothermal carbonization, chars, sanitation, renewable energy IntroductionTwo of the key issues facing more than 2 billion people in developing countries are poor sanitation and energy scarcity. Having missed the Millennium Development Goals' targets by wide margins, achieving access to adequate and equitable sanitation, ending open defecation/untreated faecal wastewater and increasing the share of affordable, renewable clean energy by 2030 now constitute the key targets of the recently adopted Sustainable Development Goals 6 and 7 (1). Annually, an estimated one billion tons of faecal wastewater is generated (2) and as much as 90% of this is discharged untreated (3, 4). Open defecation is still practised by almost one billion people, and about 2.4 billion people still lack access to improved sanitation (5). The consequences of poor sanitation are pervasive. Open defecation fields (which serve as breeding sites for insects, vectors/disease pathogens), odour nuisance, exposure to human faecal biowaste (HBW) during manual pit emptying and the indiscriminate disposal of this waste intosurface water, open drains, near slums and other fragile settlements constitute serious public health and environmental risks. Faecal contamination of drinking water resources is primarily responsible for the high infant mortality rates due to waterborne diseases such as diarrhoea, which kills 700,000 children per year (6). Aside the environmental and health impacts, experts estimate that lack of access to sanitation cost the global economy US$223 billion in 2015 -based on an economic valuation of the costs associated with premature death and loss in productivity, the healthcare costs of the sick and time forgone due to lack of access to improved sanitation (7).In common with poor sanitation, energy scarcity affects the least well off; an estimated 90% of people in developing economies lack access to reliable energy supplies (8). More than two billion people rely on firewood, charcoal and other related forest biomass to meet...

Preparation and Modification of Biochar Materials and their Application in Soil Remediation

“…Compared with the pyrolysis, HTC does not require drying step and has a higher biochar yield [15]. The advantages of microwave carbonization are controllable process, no hysteresis, rapid heating, and energy efficiency [16,17]. However, biochar prepared through HTC and microwave contained high concentrations of organics, which are not actually considered soil remediation material.…”

Characterization of fecal sludge as biomass feedstock for thermal treatment in the southern Indian state of Tamil Nadu

“…The average moisture content of the septage characterized in this study exceeded 97%. Thermal processes designed to handle high moisture content such as hydrothermal oxidation ( Miller et al ., 2015 ; Qian et al ., 2016 ) or hydrothermal carbonization ( Afolabi et al , 2017 ) may be better suited for the treatment of this septage. Challenges associated with hydrothermal processes include scaling down to compact decentralized systems and the need for pre-thickening the feedstock to 5–10% solids ( Tyagi & Lo, 2013 ).…”

“…Innovative sanitation treatment approaches under development aim to recover energy from onsite waste systems through processes including combustion ( Sellgren et al ., 2017 ), gasification ( Onabanjo et al ., 2016 ), smoldering ( Yermán et al ., 2015 ), hydrothermal oxidation ( Miller et al ., 2015 ) and hydrothermal carbonization ( Afolabi et al ., 2017 ). Key figures of merit for biomass feedstock include total solids (TS) content and calorific content.…”

Wards a Sustainable Incentive to Open Defecation Eradication

“…The incinerator ash residue from sewage sludge incineration, when mixed with dried sludge can be applied as additives in making construction materials like tiles, bricks, artificial lightweight aggregates, and cement material (Semiyaga et al, 2015). The frontiers of reuse, in the light of new interest in green and circular economy and improvements afforded by technology, have extended to applications such as high energy char, which is a product of the microwave thermochemical conversion process between 180°C and 200°C, and can be a greener alternative to firewood and charcoal -the main cooking energy sources of poor households in Africa, and eliminating associated environmental impacts (Afolabi et al, 2017). Moreover, as canvassed in Mohson et al( 2017), biogas which is a mix of methane, carbon dioxide and other gases in small quantities which can be converted to heat or electricity (Jouhara et al, 2017;Malinauskaite et al, 2017) can be recovered from faecal waste.…”