AD: application Flashcards
history of its use
AD has been used for several decades to stablise sludge residues from wastewater treatment
in enginnering terms, a tried and tested process, and energy yields for sewage sludges are well established
AD were built for organic fraction of MSW from the late 1980’s
what are the different process types
wet, dry, mesophilic, thermophillic, one stage, multistage
what are biogenic sources and production in Europe in 2005
LF sites are at present the main producers of biogas with 3,172.7 ktoe
waste water treatment plants produce 932.4 ktoe
agriculture produced 854 ktoe
primary energy production grew by 15.9% between 2004-2005 with the major growth in agricultural biogas (+58%) and biogas from MSW (+12.8%)
what is the contribution of AD plants treating municipal waste to meet targets
In Europe, 124 plants (2006) (2 in uk) (168 BMW/OFMSW with codigestion)
> 3900000 tonnes per year (2006)
6200000 with codigestion
in Europe, 244 installations (2014)
>7750000 tone per year of capacity (2014)
total AD facilities in Germany alone is around 8000 in 2011
what MSW can be digested
BMW
source segregated food waste
source segregated organic fraction of MSW
commercial organic waste (food waste from businesses, restaurant waste, or catering wastes from institutional kitchens such as schools, hospitals, universities, office blocks, prisons etc.
waste from certain munipally located industries e.g. food processors and packagers
what are the objectives for different treatment approaches
source segregates waste (BMW)
- high quality fertilizer product
- renewable energy
residual waste
- reduce organics to comply with the landfill directive, can give a stabilized (inert) products
- renewable energy
- can only produced a low quality compost (can not be used in agriculture)
- maximize reuse of other waste components in a dirty MRF
commercial systems: source segregated and residual waste
- Europe particularly leading the wat
e. g. Dranco and kompogas : continuous, high solids, thermophilic, single stage
Biocel
- batch, high solids, mesophilic
BTA
- low solids, upflow sludge, blanket, continuous
source segregated waste treatment
- pre-treatment and post treatment are minimized
- however waste streams need to be particularly pure
- also, still need to reduce the particle size
- liquid fertilizer is produced
what are the benefits of source segregation
- removed wet and putrescible waste from the rest of dry waste
- reduces vermin and smell problems
- recycling of drying wastes easier
- biofertiliser is free of contaminants and can be applied to agricultural land
- anticipates the EU Biowaste Directive
- keeps the process simple
example: Biocycles south shropshire demonstration plant
concenpt based on collection of domestic catering waste
separated in hh in separate lined bin
uncooked and cooked food vegetables and meat bones NO garden waste Moisture content >75% 200kg per hh per year
biocycle wet system concept e.g. komopgas- dry thermophillic, single-phase plug flwo description digestion
waste pre-heated in heat exchanger
digestor mixer works intermittently and slowly moved waste along reactor
digestor operates at 54C with a HRT of 15-25 days
digestate separated in liquid fertilizer and fibre for composting
plug flow design guareetess a minimum retention time
Residual waste treatment
- the digestor must be part of an integrated package
what are the important factors affecting decision making
waste collection (source segregated or mixed)
retrofitted MBT or new MBT (Mixed)
choice of feedstock
energy balance
fertilizer value and markets for digestate
odour generation and gas cleaning
downstream processing, storage and maturation of digestate
compliance with the animal by-products regulation (ABPR)
proximity principle
