The florafuel Procedure

Outline of the florafuel Procedure

Bioenergy from Humid Biomass

According to estimates of the German Advisory Council on the Environment (Umweltrat), around 100 million tonnes of landscape conservation materials and biomass waste accumulates in Germany per year. The Council states that 65 percent of this could be used to recover energy. Processing a mere ten percent would make around 7,400,000 MWh of regenerative fuel available per year. This corresponds to a fuel oil equivalent of approx. 750,000,000 litres per year and an annual CO2 reduction of 1,900,000 tonnes (without taking into account the energy in the press juice and energy consumption). 

With the florafuel Procedure, almost all kinds of humid biomass can be treated to generate CO2-neutral energy sources and fuels. Biomass types suitable for processing include grass and marshland cuttings, roadside cuttings, foliage, silage and fermentation waste (wet fermentation). 

The florafuel Treatment Process

The treatment or conversion of biomass types to generate energy sources is carried out in several working steps (cf. Diagram 1) in florafuel plants. Firstly, the biomass lots are classified according to entry humidity content, cutting length, structure, washability and percentage of foreign bodies. Following this, the material is washed, shredded and then mechanically dried with very low energy consumption. The washing process flushes out mineral particles such as stones, sand and earth as well as metals. It also significantly reduces those substances generally found in stalk material which are harmful when set free during combustion, such as chlorine and potassium.

Following thermal drying, during which the waste heat from industrial and biogas plants may be used, the material is condensed to form briquettes and pellets. The fuels generated in this way are CO2-neutral and may be used as single lots (grass, foliage, etc.) or as mixed fuels (wood/grass pellets or wood/foliage pellets, etc.) for heat and electricity generation. 

Diagram 1: florafuel process steps for treating humid biomass

 

The florafuel Procedure allows different processes to be used depending on the type of biomass to be treated (cf. Diagram 2). Biomass made up of stalks (for example, grass, foliage, marshland cuttings or grass silage) demonstrates a humidity content on entry of over 50 percent and is processed into fuel using the florafuel Procedure “washing, shredding, pressing, drying and compressing (pelleting/briquetting)”.

Diagram 2: Processing steps for the individual biomass types

 

Fermentation waste or similar materials are processed with reduced efforts. As transition points are arranged flexibly, a very humid biomass type, such as fermentation waste, may be pressed, dried and pelleted in the same plant. 

The prototype of the florafuel plant achieves a throughput rate of up to three tonnes per hour (grass) and, assuming the test plant runs for 5,000 operating hours per year, fuels with an energy content of around 11,100 MWh/a could be supplied, depending on the biomass type (without taking into account energy consumption).

Use of Press Water

The press water which accumulates during processing in the florafuel plant may be used in three ways, depending on the biomass feedstock. Tests carried out on the press juice from grass received the quality mark “fluid compost” in accordance with the quality and grade guidelines of the Professional Association of Bavarian Compost Producers (Fachvereinigung Bayerischer Komposthersteller e.V.). 

Furthermore, the juices can also be sent to fermentation plants to produce energy. Batch tests show a good “digestibility” of the juices and a rapid process period of up to 16 days. By comparison, the grass fermentation period in traditional NAWARO biogas plants amounts to more than 30 days. The biogas yield is approx. 617 litres in the case of fermentation of grass juice, approx. 340 litres in the case of foliage per kg of organic dry substance and a methane yield of between 56 and 62 % (cattle slurry 345 l/kg organic dry substance, grass 627/kg organic dry substance). With respect to the organic dry substance, the methane yield of florafuel press juices is thus comparable to the level of conventional biogas plants. Furthermore, the co-fermentation of juices in industrial or local authority digestion tanks in sewage plants is conceivable. The thermal process energy of the fermentation plants could be used for drying press cake.

Last but not least, the press juices may be used or processed to recover the dry substances contained within them. This is possible using simple filter technology. The dry matter recovered from the press water (between 5–8 %) is added to the product stream and therefore to the pellet production. In this way, the pellet yield in relation to the processed fresh mass increases. The residual water freed from the dry substance can be pre-cleaned directly in the plant using a biological sewage treatment and is added to the sewer system in accordance with the respective sewage laws. Alternatively, the press water freed from the dry substance may be used as fertilizer on agricultural land.

Overview of the Advantages of the florafuel Procedure

  • Expansion of the raw material base for bioenergy
  • florafuel fuels are CO2-neutral
  • Assists in achieving energy independence of cities, towns and local authorities
  • New possibility for local bioenergy generation with regional added value
  • No competition to agricultural feed and food production
  • Strengthening regional economic structure (new sources of income for farmers, compost and biogas plant operators; generation of jobs, etc.)
    florafuel fuels can be stored and transported and are capable of covering the base load.
  • Closing the regional waste loop by exploiting hitherto unutilised biomass materials
  • Potential use of waste heat from industrial and biogas plants
  • Low space requirements of the florafuel plants
  • Environmentally friendly processing of humid biomass and bio waste
  • Significant reduction of the chlorine and potassium content

    Cross references