The anaerobic
biodegradation model (ABM)1 (link) was used to
model methane emission from the slurry
present in each of the pig house sections and for extrapolation of
emissions from the slurry in outside storage. The ABM predicts organic
matter transformation to methane and carbon dioxide by simulating
(i) initial disintegration, hydrolysis, and fermentation of degradable
volatile solids (VSd) to VFA through a single first-order reaction
and (ii) methanogenesis using Monod kinetics for describing VFA conversion
by active methanogens, resulting in the production of methane and
carbon dioxide. The ABM explicitly simulates development of a methanogen
community and by default includes five methanogen populations,1 (link) which are active in different temperature ranges.
These default settings were initially chosen based on fitting to methane
productivity at varying temperatures as reported by Elsgaard et al.25 (link) Here, the numbers of methanogen groups were
reduced to three (m0, m1, and m2) to decrease computation time and
complexity during parameter estimation. In light of recent studies
on methanogen activity at low temperatures,3 (link),26 (link) VFA
substrate conversion rates (qmax,opt)
at low temperatures were reduced taking into consideration measured
methane potential curves3 (link) and implementing
of a new methanogen group (m0) (Supporting Information,Table S2 and Figure S1 ).
Enrichment of
VSd in the residual slurry remaining after slurry removal (from pig
houses as well as from outside storages) was implemented in a similar
fashion as for methanogens, which has previously been described.1 (link) Washing of the pig sections between batches of
pigs was simulated by the initial removal of slurry, leaving only
the residual mass, which was then diluted with water (70 kg pig–1), and finally removal of diluted slurry to the slurry
level before washing (but after the initial removal of slurry). This
simulation would have the net effect of reducing the amount of VSd
and methanogens present in the pit before the next batch of pigs enters
the section. Substrate (VFA) inhibition was implemented in the ABM
using a modified version of the model published by Zhang et al.,27 (link) see the Supporting Information,Text S1 .
biodegradation model (ABM)1 (link) was used to
model methane emission from the slurry
present in each of the pig house sections and for extrapolation of
emissions from the slurry in outside storage. The ABM predicts organic
matter transformation to methane and carbon dioxide by simulating
(i) initial disintegration, hydrolysis, and fermentation of degradable
volatile solids (VSd) to VFA through a single first-order reaction
and (ii) methanogenesis using Monod kinetics for describing VFA conversion
by active methanogens, resulting in the production of methane and
carbon dioxide. The ABM explicitly simulates development of a methanogen
community and by default includes five methanogen populations,1 (link) which are active in different temperature ranges.
These default settings were initially chosen based on fitting to methane
productivity at varying temperatures as reported by Elsgaard et al.25 (link) Here, the numbers of methanogen groups were
reduced to three (m0, m1, and m2) to decrease computation time and
complexity during parameter estimation. In light of recent studies
on methanogen activity at low temperatures,3 (link),26 (link) VFA
substrate conversion rates (qmax,opt)
at low temperatures were reduced taking into consideration measured
methane potential curves3 (link) and implementing
of a new methanogen group (m0) (Supporting Information,
Enrichment of
VSd in the residual slurry remaining after slurry removal (from pig
houses as well as from outside storages) was implemented in a similar
fashion as for methanogens, which has previously been described.1 (link) Washing of the pig sections between batches of
pigs was simulated by the initial removal of slurry, leaving only
the residual mass, which was then diluted with water (70 kg pig–1), and finally removal of diluted slurry to the slurry
level before washing (but after the initial removal of slurry). This
simulation would have the net effect of reducing the amount of VSd
and methanogens present in the pit before the next batch of pigs enters
the section. Substrate (VFA) inhibition was implemented in the ABM
using a modified version of the model published by Zhang et al.,27 (link) see the Supporting Information,
