Introduction
On a farm, biomass waste such as pruning residues, processing residues and woody cuttings is often an operating cost: it has to be collected, handled, transported or disposed of, without generating any direct economic return. Yet the same biomass, if properly valorised, can become the raw material for a supply chain able to produce electricity, thermal energy and biochar.
The energy and agronomic valorisation of waste makes it possible to turn a residual material into a farm resource, reducing dependence on external energy supplies and increasing the value generated by the ordinary management of biomass. From this perspective, biomass is no longer a by-product to be managed, but a secondary raw material to be fed into a production cycle capable of generating energy and stable carbon for the soil.
Beyond the energy and agronomic benefits, valorising waste can reduce biomass management costs and replace part of the energy purchased from outside, turning a cost item into a productive resource.
From waste to farm-made pellet
Not all agricultural biomass is equally suitable for gasification.
Lignocellulosic biomass, such as pruning residues from vineyards and orchards, forestry residues, brushwood, wood chips and woody residues from green maintenance, is generally compatible with the process. By contrast, herbaceous biomass with a high silica content, such as cereal straw, rice husk or miscanthus, may present greater operational challenges and, in many cases, be better suited to other forms of valorisation, such as composting (see silica and ash).
To be used in the BioGS-1.0, the biomass must go through a preparation stage that includes:
- collection and selection of the material;
- drying down to a maximum moisture content of 10%;
- grinding;
- pelletising.
In practice, pre-drying down to about 14% is generally sufficient, since the pelletising stage helps complete the moisture reduction without requiring further dedicated steps.
Not all agricultural waste requires pelletising. Nut shells and stones, whose size is already compatible with the BioGS-1.0 feed system, can be added in certain quantities directly to the pellet mix, without needing to be pelletised themselves.
Unlike pellet intended for domestic heating, the BioGS-1.0 does not require ENplus-certified pellet. A pellet made from suitable plant biomass is sufficient, even when produced directly on the farm by a pelletising plant sized for the harvest season, which is generally concentrated between May and September.
In many farming contexts the fuel can be produced directly from farm residues, reducing dependence on purchased commercial pellet.
Thermochemical conversion of biomass: energy and biochar from a single process
The agripellet obtained in this way feeds the BioGS-1.0, with an actual consumption of about 2.4 kg/h per unit.
Inside the system, the pelletised biomass undergoes a thermochemical conversion process that combines pyrolysis and gasification. The volatile fraction of the biomass is converted into syngas, which is then used to fuel the patented Stirling engine and simultaneously produce electricity and heat. For a comparison with direct combustion, see the FAQ why turn waste into agripellet instead of burning it.
The overall energy efficiency of the system exceeds 94%, thanks to the integrated recovery of the thermal energy generated during the process. In addition to electricity and thermal energy, the process produces biochar as a solid residue: about 11-12% of the mass of the pellet consumed, with a carbon content close to 96%.
The energy produced can be used directly to cover part of the farm's needs, such as:
- irrigation systems;
- cold rooms;
- lighting;
- workshops and laboratories;
- ventilation systems;
- drying of biomass and agricultural products;
- auxiliary farm services.
Farm biomass is therefore valorised not only as a fuel, but as an energy carrier able to contribute to the independence and resilience of the farm.
To learn more about how the technology works, see the dedicated articles Biomass gasification: the thermochemical core of the BioGS-1.0 and The Stirling engine: how it works and why it is ideal for micro-cogeneration.
Biochar and carbon farming: agronomic use and carbon storage
Unlike conventional biomass combustion, in which almost all the carbon is oxidised and quickly returned to the atmosphere as CO₂, pyrolytic gasification retains part of the carbon in the solid carbon matrix. The biochar obtained from the BioGS-1.0 has a carbon content close to 96% and a low H/C ratio, characteristics generally associated with high stability in the soil.
Once incorporated into agricultural soils, it can help improve:
- water retention;
- cation exchange capacity;
- soil structure;
- microbial activity;
- crop resilience during periods of water stress.
Beyond its agronomic function, biochar is a potentially stable carbon stock for multi-decade or even centuries-long periods, contributing to the removal of carbon from the fast biogenic cycle.
This approach falls within the practices generally associated with carbon farming, that is, the set of agricultural activities aimed at increasing and maintaining carbon stocks in soils and biomass.
For the farm, this means that waste is not simply turned into energy, but also into an agronomic and environmental resource capable of generating long-term benefits.
To learn more about these aspects, see the articles:
- Soil amendments: definition, benefits and application;
- Carbon sequestration in soil: biochar stability and the H/C ratio.
The biomass-agripellet-biochar chain: a model of regional circular economy
Not all farms have the same amount of biomass available. Some produce too little residue to cover the entire energy demand of their own BioGS-1.0; others, on the contrary, have significant surpluses of lignocellulosic biomass.
The BioGS-1.0 supply chain makes it possible to separate geographically the place where biomass is produced from the place where it is converted into energy, while keeping the carbon and nutrient cycle within the same territory.
Farms with surplus biomass can turn it into agripellet through drying, grinding and pelletising. The resulting fuel can be used internally or distributed to BioGS users in the area.
Downstream of the energy conversion, the biochar produced can be returned to the biomass producers for agronomic use on their farmland.
In this configuration the biomass is valorised twice:
- as an energy carrier;
- as a carrier of stable carbon for the soil.
The cost of managing waste is thus turned into a local supply chain capable of generating energy, agronomic and environmental value. The benefits are distributed along the entire chain:
- BioGS users gain access to a local fuel that is potentially more competitive than certified commercial pellet;
- farms valorise biomass that would otherwise be a cost;
- biochar returns to the soil, closing the carbon cycle;
- the territory benefits from a distributed energy chain based on local residual resources.
Mass and energy balance: a case simulated with the calculator
A farm in Savignano sul Rubicone with a 200 m² storage building, a 200 m² heated greenhouse (double layer, 15 °C), 4,000 kWh/year of electricity consumption, an 8 kWp south-facing photovoltaic system and 20 t/year of brushwood at 30% moisture. From 20 t of brushwood you obtain:
In the case considered, the thermal demand of the greenhouse is the main sizing factor. The electricity produced is in fact almost sufficient with a single unit, while the increase in the number of systems is driven mainly by the demand for heat.
How the pellet is calculated
Pellet = Dry biomass ÷ 0.90 × 0.95
The pellet has a final moisture content of 10%, so each tonne contains 0.90 t of dry matter: this is why the dry biomass is divided by 0.90. Grinding and pelletising cause a mass loss of about 5%: this is why it is multiplied by 0.95.
| Step | Calculation | Result |
|---|---|---|
| Dry biomass | 20 t × (1 − 0.30) | 14.0 t |
| Pellet produced | 14.0 ÷ 0.90 × 0.95 | 14.8 t |
| Pellet consumed | 3 units × 1,463 h × 2.4 kg/h | 10.5 t |
| Pellet surplus | 14.8 − 10.5 | 4.2 t |
| Biochar | 10.5 t × 12% | 1.3 t |
| Carbon in the biochar | 1.3 t × 96% | 1.2 t |
| CO₂e potentially removed | 1.2 t × 44/12 | 4.5 t |
Rounded values. The 44/12 factor is the ratio between the molar mass of CO₂ and that of carbon. This is an indicative estimate of the sequestration effect and not a certified carbon credit.
How many units are needed
The thermal demand of the greenhouse (about 27,600 kWh/year) drives the sizing: with fewer units, thermal coverage drops.
| BioGS-1.0 units | Thermal coverage | Electrical coverage |
|---|---|---|
| 3 | 100% | 99% |
| 2 | 97% | 99% |
| 1 | 76% | 98% |
The estimate is preliminary and of low reliability: it depends on the assumptions about the insulation of the storage building (medium, 12 °C) and the type of greenhouse, on the moisture of the biomass and on the actual operating hours.
Related questions: how much biomass is needed to heat a greenhouse; what to do with surplus pellet and biochar.
Where the model is particularly interesting
The BioGS-1.0 supply chain is particularly interesting in settings with a continuous presence of lignocellulosic residues, including:
- wine estates;
- olive groves;
- orchards;
- plant nurseries;
- forestry businesses;
- green maintenance companies;
- agritourism farms with woody biomass available.
In all these settings, waste is already a flow of material that has to be managed. The ability to convert it into energy and biochar increases the value extracted from the same resource without changing the main farming activity.
What is needed to set up the chain on the farm
To implement a biomass-agripellet-biochar chain, the following are generally required:
- an area for collecting and storing the biomass before processing;
- a grinding and pelletising system sized for the annual volumes available;
- an area for natural or assisted drying, using the heat recovered from the BioGS-1.0;
- a storage area for the finished pellet;
- a dedicated area for biochar storage;
- periodic biochar emptying operations, approximately every 60 operating hours.
Conclusions
From an energy, agronomic and environmental point of view, the BioGS-1.0 makes it possible to integrate into a single chain the management of lignocellulosic waste, distributed energy production and the generation of biochar.
Biomass is no longer considered a residue to be disposed of, but a secondary raw material to be valorised through a chain that simultaneously produces electricity, thermal energy and a carbon material of high agronomic value.
For farms with pruning residues, woody residues or forestry by-products, the BioGS-1.0 Calculator makes it possible to estimate the energy potential of the available biomass, the expected biochar production and the corresponding indicative carbon balance. Data, formulas and sources of the calculation: methodology. More answers on the FAQ page.