Many materials originated by agriculture could be used for production of densified biomass fuels agripellet: Some of them are straw, grain hull waste, sugar beet waste, pruning, fruit stone, dry fruit waste, cork, grain, cotton, malt and tobacco waste, with obviously, woody residues. Agricultural residues refer to the portion of plant material that remains after a crop has been harvested and separated.
Primary residues are those that are the result of farm-level activities; they include items such as straw, stalks and leaves that are left over after harvest.
Secondary residues are those that result from processing , such as sugar beet pulps, cotton mill wastes, peanut shells, etc. For most crops, and said roughly, primary residues are produced in quantities approximately equal in weight to the crop production, and are already used for different purposes (soil conservation, animal feeding and litter, heating). The amount of secondary residues varies widely depending on the crop and processing methods used.

EN 14961-6 Non-woody pellets for non-industrial use This European standard determines the fuel quality classes and specifications of non-woody pellets for non-industrial use. This standard covers only non-woody pellets produced from the following raw material
Herbaceous biomass, Fruit biomass, Biomass blends and mixtures.
Standard include for specification of straw, miscanthus and reed canary grass pellets and for blends and mixtures.

The standard EN 14961 - Part 6: Non woody pellets for non-industrial use is too wide and contain lot of materials, what was not tested by CARBOROBOT, bellow we list materials, what was tested and the boiler can work with him.

All other materials, what is listed in the standard EN 14961-6 was not tested and the Producer can not give any warranty for using.

Known pellets what problematic for burning

Rape seed if it is too small and dusty - heavy smoke due to small sizes particles, and emit too much gases in short time
Rape-straw - heavy smoke, due to this have slow burning gases, due to in clean form not burn normal, must be mixed with wood min.50% for better burning in CARBOROBOT
Soya straw - heavy smoke, must be used similar to the rape-straw pellet.
seeds - wheat, corn, barley - they burn irregular, slow, they must be mixed with other good burning pellets, or wood chips, brown coal
sunflower shell - very corrodative, the boiler must be prepared with stainless steel parts in the fuel hopper.

Straw bale and straw chaff not available to burn in CARBOROBOT.

How many groups of agripellet exist?
Containing potassium and chlorine: straw, maize, energy grass, hay,
No potassium and chlorine content: rape, sunflower,soya, olives

What do we have to watch when using fuels with high potassium or chlorine content?
During the combustion of straw, maize,energy grass and rape straw, the potassium and the chlorine content combines and turns into a salt that appears to be a white-brownish dust. This dust deposits in the pipes of the heat exchanger and in the dust-extractor, therefore the boiler has to be cleaned frequently. If the salt gets damp, it becomes extremely corrosive. In order to avoid the condensation, the return water temperature must be kept above 60-70C using an automatic mixing valve. The boiler must not be operated with cold (below 60C) water for prolonged periods. These pellets generally have glassy cinder stucked together in lumps.

What do we have to watch when using agripellets that do not contain potassium and chlorine?
These pellets burn without salt formation and do not pollute the heat exchanger so much. The smoke has a pleasent smell and optimal combustion can easily be achieved. The airflow plate for this fuel is generally agripellet/coal (No1)

Sometimes these pellets burn and gassify similarly to the wood pellets and therefore the wood pellet airflow plate performs better. In this case, the operator has to decide whether the boiler is well controllable and burns without smoke with the wood pellet plate. (wood pellets with lots of bark and large ash content, or reed pellets burn better generally with wood pellet setting) These fuels produce a light and loose ash.

What do we have to watch when using oily agripellets?
These fuels have high calorie content and require a lot of air. Sometimes these pellets burn and gassify similarly to the wood pellets. The oily agipellets may produce a dark-grey smoke that smells unpleseant. The boiler should be optimized to eliminate the dark smoke, but the unpleseant smell sometimes can’t be avoided. These fuels produce a light and loose ash.

The sunflower seed and refuse grain pellets strongly corrode the boiler tank. Consult the manufacturer before using them as necessary to incorporate stainless steel components.

How do we store the pellets?
In any case, the pellets must be kept dry, otherwise they disintegrate. Do not store the pellets for years ahead without stirring it, because pests may proliferate in the pile. Protection required against rodents (poison or cat)

Can bricket, straw-bricket or wood bricket be used?
Brickets can not be used except in the wood chamber of Farmer type, burnt manually just like logs.

There is a lack of wood-based raw materials for pellet production, or it is expensive. In many European countries more straw and grass material than wood is available for the raw material for pellet production. In this context mixed pellets mean pellets that are produced from non-wood and wood materials. Currently, the most commonly used raw materials include miscanthus, straw, reed canary grass and peat. Canada is also considering the use of switch grass and alfalfa as agricultural raw materials for fuel and feed. The combustion of mixed pellets is difficult due to the ash content, its melting and slagging tendencies, and emissions.

Straw is the most important alternative material. According to estimates the straw harvest in Europe is nearly 23 million tons of dry biomass (present European usage of pellets is under 10 million tons and the production of alternative pellets about 400 000 tons). The combustion characteristics of different straw species vary. The ash content is rather high, about 5%.The characteristics of some key raw materials are shown in Table

In aspect of the heating boiler there is two main biomass pellet group:

Wood pellet made from woody materials,(mainly sawdust)
Agripellet (agropellet) made from agricultural biomass.

The most important different between the two pellet types is the ash content. The wood pellet have 05-1% ash and the agripellet have 3-10% ash. For the wood pellet designed boilers not recommend to use agripellet due to high ash contetnt. The agripellet cheaper than woodpellet.

For the agripellet using need specialy designed boiler as CARBOROBOT

Standards have been made for controlling the market quality of pellets in Europe. “Multipart standard EN14961 6 – Pellets” was published in 2010. The standard includes both wood pellets for non-industrial use (part 2) and non-wood pellets for non-industrial use (part 6). Pellet standards are targeted at non-industrial use in small-scale appliances, such as households and small commercial and public sector buildings.In “specification and classes” (EN 14961-1), classification is based on origin, source, major traded forms and properties.

Product standards for
- non-woody pellets (EN 14961-6)

Product standards are targeted for non-industrial use in small-scale appliances

The raw material for agropellets can be
- woody biomass,
- herbaceous biomass,
- fruit biomass, or
- biomass blends and mixtures

Pellets are usually manufactured in a die
The total moisture is usually less than 10% of their mass

BIOfuel pellet EN 14588, term 4.23
- densified biofuel
- made from pulverised biomass with or without pressing aids
- usually with a cylindrical form,
- random length and typically 5 to 40 mm, with broken ends