TY - BOOK
T1 - Minimisation of odour from composting of food waste through process optimisation - A Nordic collaboration project
AU - Sundberg, Cecilia
AU - Jönsson, Håkan
AU - Romantschuk, Martin
AU - Arnold, Mona
AU - Norgaard, Erik
AU - Smårs, Sven
PY - 2009
Y1 - 2009
N2 - The aim of this project was to develop recommendations regarding how
composting processes for the treat ment of source-separated food waste in
Nordic countries should be designed and implemented in order to:
Minimise the risk of odour problems with the process
Minimise the risk of odour problems with the finished product
Achieve an efficient and reliable process
Achieve a high and uniform product quality.
The hy pothesis for the project was th at total odour emissions from the
composting process and the risk of odour from the finished com post
product could be m inimised if the process turnover rate and decom position were to be maximised.
In the project, incom ing biowaste and c omposting processes were investigated at three full-scale composting plants (NSR in Sweden, YTV in
Finland and IVAR in Nor way) and at an experi mental reactor (S LU in
Sweden). The results showed a strong correlation between pH an d odour
in compost pore gas. At lo w pH values (below 6.0) the odour concentration was very high, from 70 000 to over 2 million ou E/m3
, whil e at pH
>6.7 it was at most 44 000 ouE/m3
.
The biowaste collected wa s consistently acidic, with pH between 4.7
and 6.0. Tests confir med previous results that the de composition process
proceeds much more slowly at low pH (<6) if the tem perature is allowed
to rise above 40°C. Howev er, if the temperature is kept below 40°C, decomposition is intensive, which causes the pH to climb rapidly. When the
pH has incr eased to over 6.5, but not before, the te mperature should be
allowed to increase to around 55°C, since this maximises the decomposition rate.
The most im portant recommendation as regards decreasing o dour
problems in composting of food waste is to control the process so that the
pH is increased rapidly. This can be achieved by intensive ventilation at
the beginning of the process, whic h promotes cooling and increases the
oxygen suppl y. The pH can also be increased through addition of pHincreasing material such as co mpost or wood ash w ith a hi gh pH. This
minimises the am ount of intensely m alodorous acidic com post in the
system. In addition, it m aximises decomposition from the very beginning
12
of the process, which leads to m aximisation of the proportion of total
odour em itted in the encl osed part of the co mposting plant, where the
odours can be treated before being released to the environment.
The am ount of readily av ailable energ y in fo od waste is very hi gh,
while in stable and well-matured co mpost it is low. Therefore, a large
amount of energ y m ust b e released during com posting. This energ y is
largely used for evaporating water from the compost. Since food waste is
very energy-rich, the amount of water in the inco ming waste is not sufficient to allo w evaporation of t he am ount required to cool the c ompost
sufficiently to beco me sta ble. To ach ieve optimal p rocess speed in the
enclosed part of the com posting plant, it should t herefore be possible to
add water. Otherwise the degradation process halt s until a sufficient degree of cooling is achieved, e.g. through water in the form of rain or snow
being added during post-process maturation.
AB - The aim of this project was to develop recommendations regarding how
composting processes for the treat ment of source-separated food waste in
Nordic countries should be designed and implemented in order to:
Minimise the risk of odour problems with the process
Minimise the risk of odour problems with the finished product
Achieve an efficient and reliable process
Achieve a high and uniform product quality.
The hy pothesis for the project was th at total odour emissions from the
composting process and the risk of odour from the finished com post
product could be m inimised if the process turnover rate and decom position were to be maximised.
In the project, incom ing biowaste and c omposting processes were investigated at three full-scale composting plants (NSR in Sweden, YTV in
Finland and IVAR in Nor way) and at an experi mental reactor (S LU in
Sweden). The results showed a strong correlation between pH an d odour
in compost pore gas. At lo w pH values (below 6.0) the odour concentration was very high, from 70 000 to over 2 million ou E/m3
, whil e at pH
>6.7 it was at most 44 000 ouE/m3
.
The biowaste collected wa s consistently acidic, with pH between 4.7
and 6.0. Tests confir med previous results that the de composition process
proceeds much more slowly at low pH (<6) if the tem perature is allowed
to rise above 40°C. Howev er, if the temperature is kept below 40°C, decomposition is intensive, which causes the pH to climb rapidly. When the
pH has incr eased to over 6.5, but not before, the te mperature should be
allowed to increase to around 55°C, since this maximises the decomposition rate.
The most im portant recommendation as regards decreasing o dour
problems in composting of food waste is to control the process so that the
pH is increased rapidly. This can be achieved by intensive ventilation at
the beginning of the process, whic h promotes cooling and increases the
oxygen suppl y. The pH can also be increased through addition of pHincreasing material such as co mpost or wood ash w ith a hi gh pH. This
minimises the am ount of intensely m alodorous acidic com post in the
system. In addition, it m aximises decomposition from the very beginning
12
of the process, which leads to m aximisation of the proportion of total
odour em itted in the encl osed part of the co mposting plant, where the
odours can be treated before being released to the environment.
The am ount of readily av ailable energ y in fo od waste is very hi gh,
while in stable and well-matured co mpost it is low. Therefore, a large
amount of energ y m ust b e released during com posting. This energ y is
largely used for evaporating water from the compost. Since food waste is
very energy-rich, the amount of water in the inco ming waste is not sufficient to allo w evaporation of t he am ount required to cool the c ompost
sufficiently to beco me sta ble. To ach ieve optimal p rocess speed in the
enclosed part of the com posting plant, it should t herefore be possible to
add water. Otherwise the degradation process halt s until a sufficient degree of cooling is achieved, e.g. through water in the form of rain or snow
being added during post-process maturation.
KW - biowast
KW - pH
KW - olfactometry
U2 - 10.6027/TN2009-561
DO - 10.6027/TN2009-561
M3 - Report
SN - 978-92-893-1904-1
BT - Minimisation of odour from composting of food waste through process optimisation - A Nordic collaboration project
CY - Uppsala
ER -