Agricultural waste – the optimum biomass solution?

27/03/24

Mogens Slot Knudsen, Briquetting Expert at C.F. Nielsen A/S, explains why agricultural waste could be the best solution to preventing deforestation and increased biomass costs.

Within thin the last decades, biomass has becomean important element in many countries’ energy strategies. As one of the renewable energy sources, biomass was a driver in helping countries reduce their carbon dioxide emissions and this continues to be so.
It all started in Scandinavia and now, using biomass for fuel is common in countries, mainly in Europe but also globally. Typical raw materials are wood chips, wood briquettes and wood pellets, however, these raw materials are becoming commodities and with the increasing demand in Europe, biomass has become a scarce resource, which has led to a geographical change in the way biomass is produced — mainly pellets — as it is now being produced in countries where the biomass is cheaper. Producing biomass in one country and shipping it around the world will not be a sustainable solution in the long-term.
The higher utilisation of wood-based biomass will ead to reduced supply and higher prices. In other regions like Africa, the use of wood for fuel and cooking has led to deforestation. The only real alternative to avoid this negative trend seems to be to use agricultural waste already available in large quantities, but that is currently underutilised.
In fact, in many developing countries agricultural waste is being burned in fields instead of being used as fuel. In China, India, and other countries it is now prohibited to burn agricultural waste in the field, and these countries are looking for better alternatives.

New technologies are onstantly being developed and are available for agricultural waste. C.F. Nielsen has been working with many of these new technologies for several years; briquetting has many advantages. C.F. Nielsen produces high-quality briquetting equipment that can densify different types of biomass to create high quality briquettes, reducing volume drastically.
The briquettes become a uniform product with low moisture content, meaning reduced transport expenses. Burning briquettes in efficient stoves also reduces overall fuel consumption. No additives are usually needed in our briquette production. To new technologies such as gasification and biofuels, briquetting has added advantages. In the following cases, we outline the ways briquettes from agricultural waste are being used or can be used in a combination of old and new technologies.

Bagasse

Sugar production is largely based on sugar cane as raw material. After the sugar cane has been crushed and the sugar has been extracted, the remaining material called bagasse comes out as a waste. Part of the bagasse is typically burned at the sugar mill for the site’s own energy needs, but often the remaining material is simply dumped in nature, creating the risk of polluting the groundwater and water streams. This surplus could instead make briquettes for other energy purposes. Before briquetting, the drying and downsizingof the bagasse is needed.

As the sugar mills are getting increasingly bigger, the amount of bagasse being dumped is also increasing and making this market extremely interesting. We believe mechanical briquetting presses are the right choice for briquetting bagasse.

Hemp

One of the most recent agricultural waste opportunities has emerged in the hemp and cannabis industry in North America. Prohibition prevented mass production of hemp products for decades, but recent legalisation of cultivation and production of hemp leaves mountains of hemp waste material.
In 2019, the by-products coming from this industry was estimated to be one million tons in North America alone. How to convert this raw material into something beneficial is still an open question and the key players in the industry are busy identifying channels for usage. As a result, C.F. Nielsen has experienced an increasing interest from hemp manufacturers wanting to explore briquetting.
It turns out that this raw material makes a high-quality briquette, which can be used as a biomass fuel product in several different industries.

Gasification

Very simply gasification is a kind of incomplete combustion. By reacting organic or fossil fuel-based material at high temperatures >700°C and limiting the amount of airflow, you generate a gas called ’syngas’; this syngas can be used for the production of hydrogen and electricity.
Gasification is considered to be a source of renewable energy if the gas is obtained using biomass as a feedstock. Therefore, in recent years, gasification has been on everyone’s lips among people in the green biomass energy sector.
At C.F. Nielsen, we have done thorough testing for gasification applications over the years and it has turned out, that there are several advantages to using briquettes as a feeding source for gasifier systems. Feedstocks can consist of sawdust, wood fibres, straw, Miscanthus, bark, shells, and other biomass, as well as of paper, sewage sludge, and plastic waste. Agricultural residues make a good fuel source due to their high carbon content. Normally the gasification system needs biomass fuel to be a certain size and briquettes typically have the optimum shape. When you feed gasifiers with briquettes, the briquettes must not fall apart, and therefore a relatively high density is needed.

Sunflower husks

In some countries, the production of sunflower oil is extremely high. After extracting the oil, the husk from the sunflower seed is most often burned in the oil mills for their energy usage. But as the production facilities grow larger, they often have fewer energy requirements than what is available in the waste husks and consequently, they end up with a surplus
of waste material. Due to this, manufacturers have been searching for other uses of the sunflower husk.
One obvious way of using sunflower husks is to produce briquettes that could be sold or used in other industrial facilities for energy production. Alternatively, the briquettes could be used in local households for heating.
The quality of the briquettes produced is, in most cases, very good but depends on how the sunflower oil is separated from the seed and husk. The process varies between factories and a briquetting test should always be done first to access the result that could be obtained. Last year, C.F. Nielsen installed a high capacity briquetting plant for consumer briquettes from sunflower husks in the Balkan region.

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