Ensuring the quality and availability of fuel biomass
The main purpose of storage is to keep the biomass in good condition and in a suitable place so that it can be easily transferred to the next stages of the process of converting biomass into energy and heat through combustion.
In many cases, one of the main concerns is to keep it dry, protecting the biomass from rain, moisture, and water running through the ground. It must also be protected during the supply to the storage location, its transfer, and during access for maintenance.
Types of Storage Systems
The systems can be:
- With specific purposes and structural forms for storage, both above ground and underground;
- Adapted units, such as food silos or sheds;
- Immediately available units, prefabricated and designed for a specific type of biomass such as pellets.
Supply, storage, and extraction of biomass
The design of fuel biomass storage must consider the supply and extraction of biomass, as well as access for maintenance, which is crucial for the efficient operation of a biomass facility.
Supply
The intended method for supply must also be considered. If wood chips are to be delivered by a dump truck, the most efficient method is to deposit them directly into the fuel storage. This may require a ramp to allow truck access to the storage silo if it is built entirely or partly underground.
If the wood is to be chipped on-site, there is the possibility of storing directly within an overhead silo.
Storage
Biomass in general is a fuel with low energy density, consequently a large volume must be stored on-site if the required supply frequency is very high, and a sufficient margin safety reserve must also be maintained.
It is advisable for biomass to be stored near the combustion equipment to avoid blockages or difficulties in fuel feeding into the burner, and to be accessible to loading vehicles for supply to the storage location.
Ventilation
For most dry biomass storage, good ventilation will be necessary to prevent condensation buildup, allow for additional drying, and prevent the formation of humus and fungi that can pose a health risk if inhaled.
Good airflow can also help minimize fuel composting, leading to loss of energy content, and avoid excessive temperature buildup with the risk of fire. Studies in the USA and Denmark suggest that wood chip piles should not be built above 8 to 10 meters for this reason.
Drainage
Both in above-ground storage and underground facilities, some form of drainage should be included, in case of unwanted water ingress and also for cleaning needs of the storage, such as in cases of contamination by fungi.
Storing biomass
Factors to consider:
- Biomass does not flow as freely as oil or natural gas.
- It will generally absorb moisture if exposed.
- It may naturally biodegrade in the storage if not dry. This leads to loss of energy potential and the formation of fungi and molds.
- Efficient storage design:
- The device must keep the fuel in good conditions, particularly protecting it from moisture.
- It must also be possible to discharge the biomass into a suitable container for transport.