Overview on contents


  • Agricultural residues – an alternative biomass-fuel
  • Classification of biomass resources
  • Comparison of the heating values
  • Straw yields in comparison
  • Types and properties of selected agro-fuels
  • Wheat straw – mostly unused renewable fuel
  • Corn straw – good yields but high water and ash content
  • Corn cobs – fuel with promising future
  • Soya straw – crop with increasing potential
  • Sunflower straw – good yield but high ash content
  • Rape seed straw – good yield but difficult to pick-up
  • Short-rotation forest – alternative to crop production
  • Manure and litter from livestock farming
  • Closed-cycle agricultural production.

Agricultural residues – an alternative biomass-fuel

agro-biomass agropower energyThe technological concept of AGROPOWER biomass plants is based on using agricultural residues as fuel for energy production and therefore to contribute to the reduction of Co2 emissions. Most important to mention is that, in comparison to biogas technology which is providing mainly corn silage as input materials, agricultural residues are not competing with foodstuffs and animal feed. In general straw and other residues are still unutilised and in many cases burned on the fields.

At present the harvesting of straw with the target of utilization refers mainly to crop straw which has in terms of quantity the largest importance in Europe. Besides that, crop straw can be stored on the fields without any further treatments due to its low water content (< 20%). Wheat and barley straw represents with 66,5% of the production volume in EU-27 the most important part of straw supplying arable crops.

Production of cereals, EU-27, 2010 (%, based on tons)
- Source: Eurostat

Classification of biomass resources

According to the supply sector the biomass resources can be classified as follows:





Forestry Dedicated forestry Short rotation plantations (e.g. willow, poplar, eucalyptus)
Forestry by-products Wood blocks, wood chips from thinnings
Agriculture   Dry lingo-cellulosic energy crops Herbaceous crops (e.g. salix, poplar, miscanthus, giant reed)
Oil, sugar and starch energy crops Oil seeds for methylesters (e.g. rape seed, sunflower)
Sugar crops for ethanol (e.g. sugar cane, sweet sorghum)
Starch crops for ethanol (e.g. maize, wheat)
Agricultural residues Straw from wheat and other different crops like corn, rape and sunflower, soya, corn cobs
Livestock waste Wet and dry manure (in particular chicken litter)
Industry Industrial residues  Industrial waste wood, sawdust from sawmills
Fibrous vegetable waste from paper industries
Waste Dry lingo-cellulosic Residues from parks and gardens (e.g. prunings, grass)
Contaminated waste Demolition wood
Organic fraction of municipal solid waste
Biodegradable landfilled waste, landfill gas

Sewage sludge


Comparison of the heating values


agro-biomass agropower energy


Straw yields in comparison

The table below shows the comparison of the average grain- and straw-yields of the most important energy crops as well as the corn-straw-proportion.

  medium grain-yield t/ha  medium straw-yield t/ha  grain- straw- proportion 


 6,5  5,2  1 : 0,8


 6,8  8,9  1 : 1,3


 2,5  10,2  1 : 4,1


 3,5  2,3  1 : 0,6

Rape seed

 3,5  10,1  1 : 2,9

(Source: Energie aus Biomasse, 2009, Kaltschmitt, Hartmann, Hofbauer)

Sustainable removal of straw from fields for energy production


The sustainable removal of straw from the fields without affecting the humus content of the soil in general depends on the local soil and climate conditions. As a rule of thumb and according to scientific desk research analysis, up to 40% of the available straw may be removed from the fields for energy production without enduring damage of the soil conditions. This important fact is respected in all projects and related business plans.

Types and properties of selected agro-fuels


Wheat straw – mostly unused renewable fuel

In most of the East and Southeast European regions wheat straw in mostly unused an in many cases still burned on the fields. Due to the large-sized agricultural farms in regions along the Danube the availability of straw for energy production is evident and shows-up a capacious potential.

Properties as agro-fuel


agro-biomass agropower energy Rectangular straw bale
  • Dimension: 1,2 x 1,2 x 2,5 m
  • Weight: ~ 500 kg (high density up to 800 kg)
  • Energy quantity: ~ 2 MWh
  • Heating value: ~ 4,7 kWh/kg
  • Equivalent: ~ 200 l heating oil or 300 kg coal 





agro-biomass agropower energy
One truck with average 20 tons is equivalent to 8.000 litres heating oil








agro-biomass agropower energy

Intermediate storage on field
(Tight stacking, covered with foil)

On demand delivery to straw-biomass plant

Yields of wheat straw

agro-biomass agropower energy

YIELD t/ha
Average grain yield 6,5
Average straw yield 5,2
Grain-straw proportion 1:0,8

Bale production on the fields – approved technology

agro-biomass agropower energy

  • CASE IH LB 433 1,200 x 900 x 2,600
  • New Holland 900 x 1,200 x 2,500
  • Heston 1,300 x 1,200 x 2,500 (standard 500 kg – high tensidy 800kg)
  • Vertical strings are required

Corn straw – good yields and huge potential


Corn straw in general provides good yields and combustion properties with the minor disadvantage that corn straw contains high water content at harvesting. Due to dry weather conditions e.g. in Spain, corn straw is used for different applications and also for energy production. As the dry climate conditions in Danube Region are quite similar to Spain the use of corn straw is capable for the countries of Romania, Bulgaria and Serbia.

Advanced biomass harvesting technology is available on the market whereas a square baler is attached to a combine for collecting and packaging corn cobs, husks and leaves in just one pass with grain harvest.


agro-biomass agropower energy
  • Corn-straw proportion 1: 1,3
  • With corn yield of 6,8 t/ha ~ theoretical availability of 9 t straw
  • Restrictions related to harvesting technology
  • Pick-up problems after harvesting with combine
  • Minor experience in practise available only in southern European countries
  • New biomass harvesting technology available for collecting corn cobs, stalks and leaves in one pass





agro-biomass agropower energy


Properties for energetic use

  • High water content of corn straw at harvest but this depends on climate conditions
  • Heating value: 4,92 kWh/kg

Corn cobs – fuel with promising future

agro-biomass agropower energy

In respect of the increasing importance of the sector of renewable energy and the already shortage of wood-based biomass, new methods for harvesting and energetic use of agricultural resources are in research and development phase. As corn is among the most important crops world-wide and corn cobs show-up outstanding combustion properties the application of this forgotten fuel is of promising future. In recent years the research for cost-efficient harvesting of corn cobs with combines had been intensified. The Austrian company Lohndrusch Tschiggerl successfully developed and patented an already practise approved technology applied on the CASE AXIAL combine. This technology is of special utilisation in case corn cobs are not only to serve as biomass for combustion but also for other applications like, litter for chicken and poultry production, litter for small animals (cats, dogs, reptiles,..) and raw material for pharmaceutical and construction industry.


agro-biomass agropower energy

  • 1 ha corn cobs are equivalent to 700 litres up to 1.100 litres heating oil
  • Excellent fuel properties
  • Bulk density of corn cobs is comparable with wood chips made from spruce (160 - 170kg/m3)







agro-biomass agropower energy


Advantages for storage and energetic use

  • Storage on field eventually with foil cover
  • Corn cobs may be baled with straw baler
  • Crude ash content 2,4% of dry matter (like poplar wood)
  • Heating value: 4,82 kWh/kg

Approved and patented Austrian harvesting technology

agro-biomass agropower energy

  • Approved and patented Austrian harvesting technology developed by farmer Franz Tschiggerl in Austria
  • Adaption of axial combine necessary
  • Harvest of corn kernels and cobs in one operation cycle (harvesting time ~ 35 min/ha)







agro-biomass agropower energy

  • Cost neutral production of corn cobs as by-product of usual harvesting procedure
  • Yields of 1,2 up to 2,4 tons of corn cobs per ha depending on type of corn seeds
  • In average we calculate 2 tons/ha in our business plans

Soya straw – crop with increasing potential

agro-biomass agropower energy

Soya more and more becomes a central issue for European and especially Southeast European agriculture and food production. At present around 20mn tons hectares are cultivated in South America only for the European soya demand, which means a total import of about 25mn mt of soya bean meal and 12 mn soy beans every year. This means: An important part of the value added in domestic protein supply is taking place outside Europa.

In order to increase the dependence of soya imports the DANUBE-SOYA Association has been established in recent years. The main objective of this association is to promote the soya bean production – especially GMO-free soya cultivation – in the Countries of Danube Region. In this context the increase of soya production in Southeast Europe shall be expected with at the same time the increase of the potential for utilisation of soya straw as agro-biomass.


agro-biomass agropower energy

  • By harvesting soybean minus leaves goes through combine, residue volume less then cereals but can be left in neat windrow
  • Average straw yield: 2,3 tons
  • Heating value: 3.8 kWh/kg

Sunflower straw – good yield but high ash content

Restrictions related to harvesting technologies and the high water and ash content hamper the use of sunflower straw for energetic use at present. Using thermal power of biomass plants for pre-drying of straw might be a solution for sustainable utilization of the resources.

agro-biomass agropower energy

  • High grain-straw proportion 1: 4,1
  • With average sunflower yield of 2,5 t/ha ~ 10 t straw
  • Restrictions related to harvesting technology
  • High harvesting level of combine and pick-up problems
  • Minor experience in practise available







agro-biomass agropower energy


Properties for energetic use

  • High water content of stalks at harvest
  • Drying after harvest necessary
  • 10% ash content
  • Heating value: 4,39 kWh/kg

Rape seed straw – good yield but difficult to pick-up

Rape seed straw in general provides good yields and combustion properties. The harvesting technologies need to be improved in practise. First applications of some companies show-up realistic potential of rape seed straw for future energy use.


agro-biomass agropower energy

  • High grain-straw proportion 1:2,9
  • With average rape seed yield of 3,5 t/ha ~ 10 t straw
  • Harvesting effects small-sized stalks and threshed husks
  • Losses when pick-up 50 – 80%
  • Realistic rape straw harvest: 4 – 6 t/ha







agro-biomass agropower energy


Properties for energetic use

  • High moisture content at harvest with 45 – 60%
  • Post–harvest drying on field necessary
  • Heating value: 4,75 kWh/kg

Short-rotation forest – alternative to crop production

In areas with marginal revenues for crop production the growing of short-rotation forest is an up-and-upcoming alternative with prospective income for farmers as well as for the application as biomass fuel. In particular along the Danube River in the areas with wet soils and inappropriate conditions for crop farming, the cultivation of the species salix is a promising solution which will also be promoted in the CAP Common Agricultural Policy 2014 – 2020.


agro-biomass agropower energy


  • Usual species Poplar and Salix
  • Grown in short-rotation 2 - 3 years
  • Minor requirments for locations but optimum growing conditions on wet land (Salix)
  • Low annual production cost and minimal work input after first 2 years
  • Alternative fuel due to increasing demand of wood based biomass (wood chips)

Yields for poplar and salix


Good location

 Optimum location

Poplar 10 – 15 t/ha/y atro  16 – 25 t/ha/y atro
Salix 10 – 14 t/ha/y atro  15 – 20 t/ha/y atro
Volume fresh harvest 60 – 90 loose/ha  90 – 120 loose/ha



agro-biomass agropower energy


  • Different harvesting methods in practise
  • Manual with motor saw (for thick logs)
  • Forestry harvesting methods like wood harvester for SRF > 7 years
  • Modified combine - most cost-efficient an used in practise








agro-biomass agropower energy


  • Fresh energy wood has high moisture content (50 – 70%)
  • A media moisture content of the delivered fuel of 55% is usual in practise
  • To increase the heating value of the wood it will be pre-dried
  • Therefore the roofed fuel storage will be aerated with hot air and the belt dryer from the pellets company will be used

Manure and litter from livestock farming

agro-biomass agropower energy

agro-biomass agropower energy

Organic substances from livestock farming may also be used as fuel for combustion in agro-biomass plants. Depending on the animal housing and manure management system the organic substances are available as liquid manure, slurry or as litter (slurry mixed with straw or chipped wood).


Before take-in of the organic substances in the combustion process liquid manure needs to be separated from water and pre-dried. In terms of slurry and litter the need for pre-drying depends on the moisture content of the substances. In any case the drying of the manure and litter is a suitable option in order to make efficient use of the thermal power from the agro-biomass plant. Pre-drying of manure and litter improves the efficiency and profitability of the plant.


Moreover, the ash deriving from the combustion process is disinfected and can be used as excellent fertiliser for own farming purpose or for sale.



The table below shows the fresh manure (dung and urine) from animal production in livestock units (LU) (One LU is equivalent to 500 kg living weight; ~ one cow, ~ six pig fattening places, ~ 294 laying hens places) Cow






Availability 18 m3/(LU a) 15 m3/(LU a) 6,5t/(LU a)
Dry matter content (DM) 11 – 12% 7 – 8% 22 – 23%
Organic substances (OS)   1.760 kg/(LU a) 840 kg/(LU a) 1.070 kg/(LU a)

(Source: Energie aus Biomasse, 2009, Kaltschmitt, Hartmann, Hofbauer)


In practise the use of manure and litter from chicken production showed excellent conditions for agro-biomass projects. Below some basic figures for large laying hen farms:

 Preliminary data




heat value


Manure fresh

70% 91    

Manure dried

30% 39 3,375  










 manure (fresh)

 tons  99.645  66.430  33.215

 manure (dried)

 tons  42.705  28.470  14.235

 Plant technologies





 operation hours

 h  8.000  8.000  8.000

 Plant size (fuel consumption)






 MWh  144.129  96.086  48.043

Technical data CHP plant


 electricity production (at min heat use)

 MW  5,2  3,2  1,0

 electricity production (at max. heat use)

 MW  4,1  2,5  1,0

 heat production (max)

 MW  10,8  7,2  4,1
 MWh  86.478  57.652  32.764

 heat production (min)

 MW  0  0  0

Closed-cycle agricultural production

In the sense of a closed cycle production by application of CO2 optimised crop-rotation, growing of short-rotation forest on fallow land, use of thermal power for drying of crops as well as for farm and neighbour heating, production of agro-pellets and using the ash from biomass combustion as fertiliser on the fields, AGROPOWER biomass plants are along with the environmental guidelines within the existing and up-coming CAP Common Agricultural Policy.


agro-biomass agropower energy