Bioenergy has accompanied the development of human civilization ever since man discovered fire and the branches of plants and dry brushwood became the easiest way to keep warm, cook food and light up the darkness at night. A wide range of bioenergy is still used for these and other purposes today.

The source has taken center stage again because biomass (organic material of plant origin) and biofuels (the energy vectors obtained from the transformation of biomass) can contribute to reducing carbon dioxide emissions.

Unlike wind and solar, in fact, biofuels produce energy by combustion, like fossil sources, but the carbon dioxide they emit is the same one the plants captured from the atmosphere in the previous months or years and which - thanks to the chlorophyll photosynthesis process - they transformed into the organic matter of which they consist. Essentially, the combustion phase emits as much CO2 as was absorbed by the plants when they were growing and the net emission balance is potentially zero.

The problem is that energy is used along the bioenergy production chain, during the plant cultivation phase and the industrial process of processing primary biomass or its transformation into biofuel, potentially emitting carbon dioxide and other greenhouse gases. Furthermore, if the original intended use of the land is changed to start growing biomass for energy purposes, this could also trigger the release of greenhouse gases (emissions known as ILUC, i.e. Indirect Land Use Change Emissions) .

To calculate how much the net greenhouse gas emission associated with the production and use of biomass or biofuel actually amounts to, we therefore need to consider the production chain as a whole, i.e. an LCA (Life Cycle Analysis). Following this analysis, the net emission level of the bio energy source is compared with that of the fossil fuel that would replace it and its potential for reducing greenhouse gas emissions is assessed.

The LCA revealed that in some cases the biofuel production chains that use specially cultivated biomass (called first generation biofuels) may only achieve a limited reduction of greenhouse gas emissions compared to traditional fossil fuels.

Furthermore, if first-generation biomass is used, there may be another negative aspect: producing an increasing quantity of biofuels risks competing with the production of foodstuffs, subtracting arable land or allocating otherwise usable crops to the production of energy.

It is therefore appropriate to make a careful preliminary assessment of the impact on the life cycle of the supply chain used and certify the sustainability of production. In recent years, moreover, we have begun to focus on developing advanced-generation biofuels produced from feedstocks that do not compete with food production chains: e.g. lignocellulosic biomass from waste agricultural or algae that can be cultivate in tanks.

Alongside these advanced biofuels there are fuels produced from waste and residues (e.g. the organic fraction of municipal solid waste, used vegetable oils, biological sludge from urban water purification plants). Furthermore, biogas and biomethane can also be produced by capturing and recovering landfill gas and biogas generated from farming. These fuels produced from waste and residues can be classified as advanced biofuels according to the feedstock used and their inclusion is subject to the current regulations.

Eni has been running projects in these sectors for a long time. Agreements have recently been signed to receive used cooking oils with which to feed the biorefineries of Venice and Gela and produce quality biofuels thanks to Eni's proprietary “Ecofining” technology. In Gela itself, Eni recently started a pilot plant for transforming the organic fraction of solid urban waste into bio oil. In Ragusa, furthermore, an experimental algal biofixation plant is in operation which captures CO2 by photosynthesis using natural microalgae, and studies are underway with the Polytechnic of Turin on new types of photobioreactors to increase the productivity of this supply chain.

These are examples not only of how we can produce energy vectors that reduce greenhouse gas emissions, but above all of circular economy, or how waste can be used to obtain a new product, avoiding the use of new natural resources and reducing the volume of waste destined for traditional disposal processes.

Several circular economy initiatives are being considered by Eni that envisage the reuse of different types of waste (mixtures of diverse plastics, the dry component of non-hazardous urban and special waste, carbon dioxide itself) for the production of energy carriers. 

Advanced biofuels have multiple benefits. The first is that they do not compete with agricultural production for the food market. The second is that they often achieve a much lower net greenhouse gas emission balance than the traditional fuels they replace or some of the first generation biofuels.

Finally, all biofuels (both first generation and advanced) can be mixed with traditional fuels, thus helping to immediately reduce greenhouse gas emissions without having to wait for expensive adjustments to current energy transport, storage and distribution systems and existing engines.

Like many other decarbonization tools, biofuels and waste fuels are currently penalized by cost, which varies depending on the technology and its maturity. But research and development, economies of scale or a tightening of greenhouse gas emissions standards could in the future reduce and in some cases close the competitive gap with fossil fuels.

Energy Sector Integrated Technical Studies Eni, Development, Operations & Technology.