THERMOPHILIC SOLID STATE ANAEROBIC DIGESTION OF OFMSW IN SEQUENTIAL

BATCH REACTORS

NATAŠA BELŠAKScientific Research Centre Bistra Ptuj

SI-2250 Ptuj, Slovenia.

Mauritius, September 2011

Introduction

City Municipality of Ptuj introduced a Local programme for Environment Protection in the entire municipal area.

Part of it is CONCEPT OF THE ENVIRONMENTAL PROTECTION

more effective reuse of municipal waste

reduce amounts of waste that is being disposed

Material and Energetic Use of the Biological Part of Waste in the Region.

Anaerobic digestion process

Introduction

Landfill CERO Gajke

For municipalities of the Lower Podravje Region, the construction of the CERO Gajke Waste Disposal Facility represents an optimal solution for the problem of municipal waste management, which isin accordance with Slovenian and EU standards in the fields of health and environment protection.

The main characteristics of the facility are:

• include 17 municipalities of the Lower PodravjeRegion - approx. 80.000 inhabitants;

• expected lifespan of the landfill: 15-20 years;• expansion over an area of 18 ha, 12 ha of which is the

landfill area;• Lowest distance from nearly settlements: 300 m.

Introduction

Landfill CERO Gajke Ptuj include:-waste collecting,-sorting line for separate collected waste,-composting facility,-dumpsite for mixed municipal waste.

Feedstock for anaerobic digestion process

- wood biomass, consisting of tree and shrub pruning and old wood,

- a large part of green waste consisted of grass cuttings, hedge trimmings,

old flowers, weeds and leaves,

- the green waste also contained food waste, mainly raw vegetable and

fruit waste matter.

Aim of the study

Investigate the anaerobic digestion process in a sequential pilot system composed of three 120 L bioreactors.

The main focus of this research is determination of the effect of the leachate recirculation on the efficiency of anaerobic digestion process.

operating conditions of the process:- thermophilic temperature level T = 53 ± 2 ° C- moisture content 70 to 80 % (solid state)

A procedure of anaerobic digestion process

aeration of input material (the temperature reached may exceed 70 ° C)

- sanitation (pathogen reduction)- reduction of lightly degradable substances

Aerobic phase

Anaerobic phase

• substrate irrigation with sewage sludge- ensure adequate moisture in the reactor,- addition of inoculum in the reactor,- addition of nutrients

• temperature control using heating cable and on - line temperature of material monitoring by means of temperature sensors,

• leachate recirculation- pH regulation,- humidity providing,- nutrients cerirculation and dilution of potential toxic substances.

Feedstock analysis

determination of:- water content,- pH value,- Kjeldahl nitrogen,- total organic carbon.

Moisture content/% pH TNK/% s.s. TOC/% s.s.

Feedstock 58,0 ± 10,0 7,0 ± 0,7 0,67 ± 0,23 30,7 ± 6,0

Bioreactors and equipement

Bioreactors and equipement

Monitoring of the anaerobic digestion process

Produced biogas collecting (bags of different volumes: V = 10 L, 25 L, 40 L and 100 L)

Produced biogas flow monitoring

Monitoring of the anaerobic digestion process

Monitoring biogas composition(biogas analyzer Geotechnical Instrument GA2000Plus)

Monitoring leachate pH value and recirculation of leachate between the mature and new reactor

Results

The proportion of CH4 and CO2 in the biogas as a function of time

Results

Leachate pH value as a function of time

Conclusions

• Average biogas production in our research was 144.9 L biogas/kg VS ,

and the methane production was 78.25 L methane/kg VS, respectively.

• Feedstock used in the study had a high content of non-bio

degradable lignocellulose components originating from tree and shrub

pruning, old wood, grass cuttings, hedge trimmings, old flowers,

weeds and leaves, therefore only 33.5 % of volatile solids were

decomposed in anaerobic digestion process.

• Recirculation of leachate between reactors has a positive effect on

the anaerobic digestion process(increase of biogas production, there

is not necessary pH adjustment with lime, phase separation between

reactors).

Conclusions

• Our future work will focus on process optimization and feedstock pre-

treatment optimization which will be carried out by fungi with the aim of

reaching better degradation of lignocellulosic material.

• We already start with Pleurotus ostreatus cultivation on laboratory and

pilot scale in collaboration with the group of researchers specialized for

fungi cultivation.

With the strain adapted to growth on waste material.

Thank you for your attention.