The importance of anaerobic digestion within the MSW based biorefinery – Fiberight
Puri, D., Fiberight Ltd, UK
(free)
Fiberight’s process is a water-based fractionation technology involving two main steps. First, dry
recyclables (rigid plastics, film plastics, metals and glass) are separated from a dirty biomass containing
mostly food waste, paper and card, and small grits, glass, plastics and metal contaminants. In the
second step, the dirty biomass is washed to recover a clean lignocellulosic fibre product. This step
allows the solubilisation of the food waste and separation of the non-organic contaminants. The organic
laden washwater is then processed through high-rate anaerobic digestion (AD) to produce biomethane.
The clean effluent is recovered and recycled back into the process. The recovered lignocellulosic fibre
is a low ash pulp which can be used as a biomass fuel or within the manufacture of pulp moulded
products. Fiberight has also developed the technology to convert this biomass into platform sugars via
enzyme hydrolysis for the production of biofuels and biochemicals. The lignin rich solid remaining after
hydrolysis can be utilised as an engineered fuel or as a feedstock for lignin derived products. Overall
the process has the capability of diverting, recovering and upgrading over 80% of the materials in the
residual waste stream.
The process has been developed over the last nine years, with initial R&D carried out in collaboration
with the University of Southampton, UK. This initial work tested the viability of using high-rate AD to
treat the washwater so that it could be re-used in the process. This research demonstrated high
conversion of the soluble organics, measured as COD, into biomethane. The reactors ran steadily for
close to a year achieving organic loading rates of 20g/L/day and ~90% COD removal. This data and
other concurrent development work led to the decision to obtain financing for the construction of a largescale demonstration facility. This facility was built in Virginia, US in 2013 and has allowed for the
development, optimisation and demonstration of the technology at a commercially relevant scale (1/10
commercial scale). The process data, obtained from this facility, combined with the agreement of a 15
year waste supply contract from the Maine Resource Council (MRC) has led to the financing and
subsequent construction of Fiberight’s first commercial plant based in Hampden, Maine, US. This facility
is set to come online in early 2019.
