2014-02-24 07:30

Super fast digestion of waste to biogas possible

Digestion time of waste into biogas can be shortened from 30 to just three days. This is presented in a new thesis at the University of Borås.

Photo of Solmaz Aslanzadeh in the lab.

Borås Energi och miljö AB (Borås Energy and Environment Ltd) produces biogas from food waste and manure. Today the digestion process of waste to biogas usually takes up to 30 days depending on the compostition of the waste. Pure food waste decompose faster than if it is mixed with recalcitrant matter such as straw or wood waste.

Solmaz Aslanzadeh is the very first PhD student in the field of resource recovery, a unique research area, ready for dissertation. She has studied how to increase the efficiency of the anaerobic digestion of recalcitrant materials as well as reduce the time for the anaerobic digestion process, resulting in faster production of biogas.

She has studied how different microorganisms that break down the waste work and what happens when you divide the digestion process into two steps. In the first step fast-growing micro-organisms were to break down the material into soluble molecules. In a second step slow and sensitive microorganisms were to take over and continue the process of converting the soluble molecules into biogas. This new process allows an increase of the load of organic material significantly while at the same time reducing the reactor volume. The digestion time shortened considerably from 30 to three days.

Solmaz Aslanzadeh has conducted her research in collaboration with Borås Energi och miljö AB which produces biogas for vehicle fuel and for the production of electricity and district heating.


Biogas is a renewable gas that can be used as vehicle fuel and for the production of electricity and district heating. Biogas is composed mainly of methane. Biogas is produced when organic materials such as manure and food waste from households and industry is broken down by microorganisms under anaerobic conditions. The process is called anaerobic digestion and can be done spontaneously in the nature, such as in wetlands and in the stomachs of ruminant animals such as cows. How much biogas an organic material can produce depends on the nature and composition of the material. For example, one tonne of food waste yield about 400 cubic meters of methane while the same amount of waste consisting of recalcitrant material such as straw or wood waste emits significantly less methane. The most common way to produce biogas is by adding organic material in an anaerobic digester that consists of an airtight container.


Title: Pretreatment of cellulosic waste and high rate biogas production
Date : February 27, 2014 at : 10:00-12:00
Location: Room E310 , University of Borås , Allégatan 1, Borås
Subject : Biotechnology
Opponent: Irini Angelidaki , professor at the Institute of Environmental Engineering , Technical University of Denmark , Denmark
Research supervisor: Prof. Mohammad Taherzadeh, University of Borås

The defense is conducted in English .

Also read "The first PhD student in resource recovery ready for dissertation"

Text: Solveig Klug
Photo: Jerker Andersson