Coconut Shell, Rice Husk, Sawdust and EFB: Biochar Yield from Common Biomass Feedstocks

When evaluating a biomass carbonization project, one of the first questions investors ask is: How much biochar can be produced from one ton of biomass?

The answer depends heavily on the feedstock and carbonization conditions. Coconut shells, rice husks, sawdust, and empty fruit bunches (EFB) have different lignin, cellulose, ash, moisture, and fixed-carbon contents. As a result, their biochar yields can vary significantly even when processed in the same type of carbonization equipment.

For project planning, it is therefore more useful to consider a yield range rather than assume one universal conversion rate.

1. Coconut Shell: Relatively High Carbonization Potential

Coconut shell is widely regarded as a favorable feedstock for producing carbon-rich biochar. It generally has relatively high carbon content and low ash compared with many agricultural residues.

Published studies show that coconut-shell biochar yield can vary substantially depending on the reactor and temperature. For example, one review reports yields ranging from approximately 26% to more than 50% under different slow-pyrolysis conditions, while self-sustained carbonization has reported yields around 30–32%.

A practical planning assumption for industrial projects may therefore be around 30–40% biochar yield, subject to actual feedstock characteristics and process conditions.

For example, processing 1 ton of dry coconut shell could potentially produce roughly 300–400 kg of biochar under suitable operating conditions.

The relatively high carbon content also makes coconut-shell biochar attractive for applications requiring stable carbon materials.

2. Rice Husk: High Ash Content Changes the Economics

Rice husk is one of the most abundant agricultural residues in rice-producing regions. However, it behaves differently from woody biomass because it contains a relatively high proportion of silica and ash.

Reported rice-husk biochar yields vary according to temperature and reactor configuration. A review of pyrolysis studies reports approximately 30.65% yield at 350°C, 18.58% at 450°C, and 10.98% at 550°C in different experimental conditions.

More recent research focused on continuous rice-husk pyrolysis reports that optimized systems can achieve approximately 35–43% biochar yield, demonstrating how strongly reactor design and operating conditions influence the result.

For commercial feasibility calculations, operators should therefore avoid applying a single fixed yield to all rice husk. Moisture and ash content should be tested first.

3. Sawdust: Yield Depends Strongly on Temperature

Sawdust is another common feedstock because it is relatively uniform, easy to handle, and widely available in wood-processing regions.

Research data show a clear relationship between pyrolysis temperature and biochar yield. One review reports sawdust yields of approximately 30.5% at 350°C, 25.1% at 450°C, 20.7% at 550°C, and 11.8% at 650°C under the corresponding experimental conditions.

This illustrates an important trade-off: higher temperatures generally increase the degree of carbonization but reduce the mass yield of biochar.

Therefore, the optimum operating temperature should be selected according to the target product rather than simply maximizing carbonization temperature.

4. EFB: A Valuable Palm-Oil Residue

Empty fruit bunches, commonly known as EFB, are an important biomass residue from the palm-oil industry.

Research on palm-oil residues has reported EFB biochar yields of approximately 34% in some studies. Broader modeling studies also indicate that biochar yield varies considerably with feedstock and pyrolysis conditions.

EFB has the advantage of being available in large quantities near palm-oil processing facilities. However, its relatively high moisture content can increase the energy required for drying before carbonization.

This means that an EFB carbonization project should evaluate not only biochar yield but also feedstock moisture, transportation distance, drying requirements, and energy integration.

Typical Biochar Yield Comparison

As a preliminary engineering reference, the following ranges can be used for discussion rather than as guaranteed production figures:

Feedstock	Indicative Biochar Yield	Main Consideration
Coconut shell	~30–40%	High carbon content; relatively low ash
Rice husk	~20–40%	High silica/ash; moisture and temperature matter
Sawdust	~20–35%	Yield decreases as temperature increases
EFB	~30–35%	High availability but drying can be important

These ranges should always be validated through feedstock testing and pilot or commercial-scale trials. Published results can differ because researchers use different temperatures, residence times, heating rates, reactors, and definitions of biochar yield.

Why Yield Is Not the Only Metric

A higher biochar yield does not automatically mean a more profitable project.

For example, a lower-temperature process may produce more solid biochar, while a higher-temperature process may produce less biochar with different carbon characteristics and potentially different market value.

Project developers should therefore evaluate at least four indicators together:

Feedstock-to-biochar yield + biochar quality + energy consumption + selling value.

For carbon-removal projects, additional factors such as carbon content, carbon stability, lifecycle emissions, storage pathway, and measurement and verification requirements also become important.

Conclusion

Coconut shell, rice husk, sawdust, and EFB can all serve as valuable biomass feedstocks for carbonization, but their conversion rates are not interchangeable.

As a broad starting point, many industrial projects may work with biochar yields in the 20–40% range, while actual performance depends strongly on the specific feedstock and process design.

For this reason, the best approach is to test the local biomass before finalizing charcoal making equipment specifications and financial projections. By matching feedstock characteristics, carbonization temperature, reactor design, energy recovery, and biochar market requirements, biomass processors can optimize not only how much biochar they produce, but also the overall value of the carbonization project.