A complete plant with press, bale wrapper and conveyors consumes no more than 10-40 kW/h. Which comes out as low as approximately 1-1,5 kW per finished bale.
The low energy consumption owes to the special patented construction of the press. The functions of the press are electro-hydraulically powered. The press chamber has rotating sides and the feeding mat rests on rollers with ball bearings.
Thanks to the lack of oxygen inside the round bale there is no fermentation occurring inside. Storage is therefore without risk of build-up of methane gas. Poisonous substances can not be leached, since the stretch film effectively restrain all water from penetrating inside the bale (provided that the bales aren't submerged in water).
The stretch film and the net in which the bales are wrapped consist of polythene, which converts to carbon dioxide and water when incinerated. The plastic film is thin, only 25-30 µ and it constitutes only 0,1-0,2% of the total weight of the bale. A roll of stretch film weighs approximately 17 kg and is sufficient for approximately 18 bales.
The net is made of environmental friendly polythene. A roll of net weighs approximately 30 kg and is sufficient for approximately 100 bales.
The stretch film, although thin, is very tough. This ensures the hermetic enclosure of the material, which prevents the escape of litter as well as stops the degredation processes. The waste is compressed and wrapped with stretch film, into airtight bales. Without oxygen the processes of fermentation and degredation cannot start.
Degradation of waste involves two different processes; aerobic and anaerobic. In the aerobic phase the main degradation is oxidation reactions which produce CO₂. Combustion and thermal degradation can be the consequence of this phase.
During the anaerobic degradation, three metabolically different groups of bacteria become active and result in hydrolytic, acetogenic and finally methanogenic degradation. This biodegradation process in which the organic substances are acting as a nutrient as well as an oxidation agent is a result of coordinated action of many different bacteria species in sequential reactions.
Any disturbance in such a consecutive system can delay or accelerate some of the biochemical step reactions and this affects the degradation rate and energy/mass losses in the stored material. By preventing oxygen and water from penetrating the waste, Flexus baling system offers such a disturbance, thus more or less halting the biochemical process.
The first tests of storing waste in round bales were carried out by the University of Lund in Sweden. These findings has been confirmed by similar independent institutions in other countries.
The gas and temperature development, material and energy losses in the stored bales were measured.
Three different types of waste were stored, RDF (shredded), source separated waste and unsorted household waste, MSW.
A short initial period of aerobic degradation, until residual oxygen was consumed was followed by very stable conditions. No considerable temperature increase or methane production were observed even after one year and most biological and oxidation reactions were virtually stopped.
In order to study the effect of particle size, shredded household waste was used in the same way. However, formation of methane was not observed in this case either.
The graph below shows the gas and temperature development for one of the bales used in the study by the University of Lund.
|Gas & temperature development in stored waste (MSW), Bale no. N1|
|Weight of bale N1 (14.2.95)||976 kg||pH in leachate||4.2|
|Total mass loss (8.8.95)||8 kg||pH on surface of waste||5.5|
|Material||Household waste||Moisture (wt%)||45|