AGROEKO

Aerobic fermenter EWA

DETERMINATION

EWA fermenter (Ecological Waste Apparatus) is certified device for processing of biodegradable waste (BDW), including sewage sludge and animal products according to Edict 1774/2002 EC.

CONSTRUCTION

EWA fermenter consists of thermically insulated operation space, system of injectors for intensive airing of the fill, system of fill shovelling consisting of segmented floor and bucket (pocket) conveyer placed on the inside of the fermenter, and integrated device for loading and unloading. All technology points are placed inside ISO 40track container (ALL IN ONE).

EWA fermenter is protected by edict, doc. No. 295922. On November 16, 2005 an application was handed in at European Patent Office (EPO) named “The method of conversion of biodegradable hygienically non-stabilized substrate into hygienically stabilized product”. Beside this patent, four utility models, also registered by the ÚPV (Industrial Property Office) are used for the production of the fermenter. The fermenter is certified by State test-room of agricultural, forester and food-processing machinery in Prague, Certificate No. 6/2006, dated May 30, 2006.

PROCESSING PRINCIPLE

Mixture of biodegradable waste and structural (liquid-absorbing) biomass is loaded in the operation part of the fermenter. Optimal fill humidity (50-60%) and disposal of air oxygen activate the metabolism of aerobic bacteria. Aeration of the fill is done by airing and shovelling inside the fermenter. High level of metabolic activity and simultaneous reproducing of bacteria is demonstrated externally by rising temperature of the fill. Intensive thermofilic aerobic fermentation runs under the same conditions in the whole fill section. This accelerates composting processes. Complex organic matters are decomposed and transformed into others. Turbulent biological oxidation runs in the fermenter due to ideal conditions. The fill temperature rises above 70ºC and proteins are gradually denatured. High fill temperatures for defined time period cause inactivation of present bacteria and pathogenic organisms (viruses, bacteria, leaven, mould, protozoons, and worms). This process is called thermofilic aerobic stabilization and hygienization of the fill. Due to high temperature the number of microorganisms is decreasing and weed seeds loose their germinating capacity. Continuing fermentation at temperatures around 50ºC and intensive fill airing enable so-called biological final fill drying.

Common mixing rate is 30% weight ratio units of sludge component and 70% weight ratio of biomass. If the biomass input humidity is low (straw, wood-shavings) the mixing rate can be up to 50:50. The unloading humidity of the fermentate used for compost production is about 40%. If the fermentate is intended for energetic purposes the final humidity is usually below 30%. The time of fill delay in the EWA fermenter depends on the character of the fill and the final product. It takes 48 – 96 hours.

EXAMPLES OF USE OF FERMENTED AND TERMOPHILICLY HYGIENIZED BIOMASS

After the thermophilic aerobic fermentation is finished the fill is stabilized and hygienized. As its qualities have been essentially changed it is further on called fermentate. It can be used as compost for agrotechnical use or compost for energetic use (biofuel).

Compost for agrotechnical use (mulch-compost)

Mulch-compost is produced by a process of controlled aerobic composting (thermophilic fermentation). It is a mixture of agricultural and forester biomass with compostable waste. Its structure is fibrous even crumby with noticeable undegraded pieces of biomass (straw, wood chips, bark). Its color is brown or brown-grey, at the production humidity it is loose it smells like mushrooms or humid forest.Certification of the product was done by CZ BIOM, Biomass Association Prague.

Compost for energetic use (biofuel)

Compost for energy recovery is a fermented mixture of BDW, made according to company standards, in accordance with Decree No. 5 / 2007 Coll. consisting of the BRO (see catalog biowaste Decree No. 341/2008 Coll.)

The company standards provides standard production process, the range of inputs, the maximum values of controlled substances, quality attributes and recommended ways of use.

Fuel is intended for combustion in boilers for solid fuels. It is suitable for biomass boiler systems, but also for coal-fired boilers. Fuel can be used in the grate boilers, but very good results are achieved by burning in boilers with fluidized bed. Incineration may be carried out individually or in combination with fossil fuels. Produced fuel usually comes in bulk form.Compost for energy recovery has crumby, lumpy and fibrous structure; the color is brown to dark brown. In the mixture the input components of biomass are obvious - parts of plants, bark, branches, etc. The maximum length of the individual pieces of the biomass is 50 x 50 x 50 mm, very thin twigs may be up to 100 mm length, occasionally up to 200 mm.

OPERATION OF THE EWA FERMENTER AND CONTROL OF THE PROCESS

The operation cycle of the aerobic fermenter is controlled on the basis of operation reading of conditions and values which characterize the aerobic fermentation. One operation cycle consists of 3 or 4 time-separated phases.

The most important phase is the fermentation itself. The intelligent control is based on measuring of these values:

• fill temperature in the whole section
• oxygen volume in the degas

The control is based on value learning during an optimal fermentation run. The principle of the control is handling of power circuits based on current values measurements. Temperature of the fill is measured by a membrane of special thermometers whose designs fit into the specific environment of the fermenter. Besides the fill temperature, temperatures of degas and fill-airing air are measured. Measured volumes of degas are temperature and volume of oxygen. Current values are recorded and assessed by an industrial computer. The control programme turns on the airing and shoveling when marginal values of measurements are reached. Volumes of oxygen and carbon dioxide in the atmosphere are in constant mutual rate. During the process of biological oxidation of organic substrates their mutual rate is changed. The volume of oxygen decreases as it is consumed. On the contrary, the volume of carbon dioxide rises, which is the final metabolite of the aerobic oxidation of carbonic substrates (Krebs cycle). Forced airing of the fill is run through injectors placed inside the operation space of the fermenter. Fresh air is driven into the fill and simultaneously air containing water vapour is evacuated. Optimal fill airing is a precondition for the progression of fermentation in aerobic conditions. If intensive airing does not bring the expected change in concentrations of the observed gases it means that the physical properties of the fill do not allow the continuation of the aerobic fermentation without reshoveling. This state may have several causes. It may be a compression (concretion) of the fill or there has been an unwanted mudding which some fills tend to. In case the airing does not secure sufficient supply of air oxygen fill reshovelling is turned on. Thus the wanted relaying of the fill occurs as well as exchange of the gases in the operation space of the fermenter. After reshovelling the fill is again sufficiently spongy and composting runs in aerobic environment.

TECHNICAL PARAMETERS

PROCESSING ELECTRIC ENERGY CONSUMPTION