Sustainable Energy Paths: Harnessing Residual Biomass Potential in Southern Italy

Biomass is primarily used to generate electricity and heat through advanced combustion and co-firing technologies, utilizing wood, agricultural residues, and municipal solid waste [1, 2]. It is also processed into biofuels like ethanol, biodiesel, and bio-oil, which are considered sustainable alternatives to fossil fuels, with biofuels from lignocellulosic materials such as wood and agricultural waste showing great promise due to their abundance and affordability [3]. Additionally, anaerobic digestion of biomass produces biogas, which serves as a renewable energy source for heating, electricity, and vehicle fuel, while managing organic waste and reducing greenhouse gas emissions [4]. Biomass is also used in combined heat and power (CHP) systems that enhance energy use efficiency by generating both heat and electricity, often in industrial settings using waste biomass [5]. Finally, biomass pellets, made from compressed organic matter like sawdust and crop waste, are used in residential and commercial heating systems due to their compactness and high energy density [6].

Among the different available biomasses, agriculture residues represent a promising source for bioenergy production. Moreover, recovering this biomass allows on one hand to reduce the great effort, capital, and labor connected to its management, on the other hand to face the issues related to its improper management that can lead to environmental damage, such as groundwater contamination from nitrate leaching, heavy metal contamination, and other ecological nuisances [7]. According to FAO data [8], the agrifood sector produces one-third of total anthropogenic GHG emissions, with the highest contribution, almost half of the total (7.4 Gt CO_2eq), due to crop and livestock production activities, followed by pre- and post-production (5.6 Gt CO_2eq) and land-use change (3.1 Gt CO_2eq). Almost 20% of emissions related to crop and livestock production activities are caused by livestock manure, whose improper management is particularly problematic for the environment due to the high release of methane that is a much more potent greenhouse gas than carbon dioxide [9].

Finally, it is worth noticing that utilizing residual biomass for energy not only helps in reducing greenhouse gas emissions but also supports habitat preservation and biodiversity by promoting proper vegetation management [10].

Due to the high contribution that energy recovery of agriculture residues may have on decarbonization at local level, the present work presents:

-    an estimation of bioenergy potential of the agriculture sector at regional level, by considering Campania region, Southern Italy, as case study;

-    the implementation of the estimated bioenergy potential in the energy mix of Campania region, to propose different future energy scenarios with reduced emissions compared to the current situation.

3.1 Energy potential of residual biomass in Campania region

By applying the method described in Section 2.1.1, the primary energy available from the agricultural residues in Campania region is calculated. For the vegetal sector a yearly production of 10.3 PJ/y is estimated, whereas animal manure could produce 80 172 373 m³/y of methane, corresponding to 2.75 PJ/y. For the vegetal sector the data about crops production is available at a province level.

The results obtained are shown in Figure 1, where the crops are assembled in macro-categories, except for olives and vine dedicated to wine production, to highlight their significant contribution.

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Figure 1. Energy potential of the vegetal sector

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Figure 2. Energy potential of the animal sector

The results show that Caserta emerges as one of the most important provinces in terms of primary energy produced by various crops, followed by Avellino. Fruit trees represent the largest source of primary energy, with Avellino and Salerno dominating in this category.

Finally, it can be noticed that there is significant variability between provinces regarding the crops providing more energy, likely reflecting the available surface, the geographical characteristics, the urbanization as well as climatic and agricultural differences within the region.

For the residues coming from the farming sector the data are available only at a regional level. The obtained results are shown in Figure 2.

The results highlight that residue coming from buffaloes’ residues are the highest source of methane in Campania region, followed by those of bovines. Production of methane from swine manure is considerably lower, though still notable, whereas it is minimal from goats and sheep.

3.2 Current energy mix in Campania

Campania's energy system shows a lack of connection between transport, heat, and electricity demands, with fossil fuels being the primary energy source (Figure 3).

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Figure 3. Campania energy mix for the base year

This indicates a lack of flexibility in the current energy system, as demonstrated in studies [19, 20]. An increase in renewable energy production could result in Critical Excess Production of Electricity (CEEP), where electricity generation surpasses consumption and system interconnection capacity, potentially leading to system collapse and increased production costs.

Heating demand, primarily met by natural gas, biomass, and oil, totals 22.71 TWh_th. Despite Campania's high geothermal potential, its use is minimal. Cooling electricity, usually a minor part of the total energy in European regions, accounts for about 10% of Campania's heating budget (approximately 2.11 TWhe) and is projected to rise to 30-70% by 2050 due to improved living standards and climate change effects.

Electricity production in Campania is mainly from:

- Conventional thermal power plants (approximately 62.7%)

- Wind (approximately 23.3%)

- Hydroelectric (5.6%)

- Photovoltaic (8.3%)

In the last 15 years, renewable energy sources (RES), especially wind energy, have become significant. By 2017, Campania had 593 wind turbines with a capacity of 1388 MWe, and other RES capacities included 784 MWe from photovoltaics, 233 MWe from bioenergy, and 337 MWe from hydro plants. In total, Campania had 31,056 RES power generation plants with a combined capacity of 2,741 MWe, producing 4,578 TWhe of electricity.

In 2017, Campania's RES power capacity represented about 5% of the national capacity, making it the eighth Italian region for renewable energy production, contributing nearly 28% of the total production in Southern Italy and the islands (7 Mtep).

3.3 Future scenarios

The 2030 scenario includes:

- Electrification of transport, through a shift to electric and hybrid vehicles with vehicle-to-grid (V2G) technology;

- Renewable energy expansion, through an increase in wind and solar energy as per regional plans;

- District Heating and Cooling (DHC), with the introduction in select areas using geothermal energy.

The 2050 scenario builds on 2030 with:

- Increased transport electrification;

- Stable thermoelectric generation;

- Advanced DHC systems, powered by CHP plants using natural gas and renewable energy (geothermal, solar thermal, biomass);

- More wind and PV installations.

Additionally, biomass utilization within the region, as assessed in earlier sections, was integrated into the energy system. Biogas produced from animal manure was intended for incorporation into the gas grid, while agricultural residues were to be gasified to generate syngas, which would also be blended into the gas grid.

3.3.1 Scenarios’ results

The demand for electric energy increases from 18.4 TWh/year in 2017 to 26.4 TWh/year in 2050, with significant growth in production from renewable sources, especially solar and wind (Figure 4). Natural gas use in power sector remains a key component until 2030, but its consumption drastically decreases by 2050, while the use of biomass and waste increases substantially.

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Figure 4. Demand and electricity production for type of plant of each scenario

The demand for heating decreases, with a strong shift towards district heating, which covers 76% of the demand by 2050 (Figure 5). The demand for cooling also increases, with district cooling covering 68% of the demand by 2050 (Figure 6). Individual consumption of natural gas and biomass for heating decreases, while solar thermal increases slightly. The consumption of electricity for individual cooling significantly decreases by 2050.

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Figure 5. Demand and electricity production for type of plant of each scenario

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Figure 6. District cooling demand for each scenario

In the industrial and transport sectors, the consumption of fossil fuels decreases, shifting towards natural gas and electricity. The use of electricity in transport grows, especially for smart charging.

CO₂ emissions reduce by almost 70% by 2050 compared to 1990 levels, with the most significant reduction coming from decreased oil use and a shift to renewable sources and waste (Figure 7).

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Figure 7. Primary energy supply for type of source and CO_2eq emissions for each scenario

3.3.2 Decarbonization potential of residual biomass

This section discusses the decarbonization potential of integrating residual biomass into the Campania region's energy system by 2050. The analysis shows that incorporating biomass can substantially increase the share of renewable energy sources, enhancing the sustainability of the energy mix and reducing greenhouse gas emissions. Specifically, the use of biomass boosts the renewable energy share to 87% (Table 3 and Table 4), significantly lowering the region's dependence on natural gas. The findings indicate a potential 72% reduction in CO₂ emissions compared to the baseline year, underscoring the role of biomass in achieving climate targets (Figure 8).

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Figure 8. Primary energy supply for type of source and CO_2eq emissions for each 2050 scenario

Biomass's contribution to combined heat and power plants is notable, offering a versatile solution that provides both electricity and heat, thus enhancing overall energy efficiency.

The implications for policy and practice are clear: developing biomass infrastructure and technology should be prioritized, with incentives for effective residue management and biomass supply. Investments in biomass conversion technologies are essential to realize the benefits outlined in the study. However, challenges such as sustainable biomass sourcing and logistical barriers need to be addressed through continued research and development.

Table 3. Fuel balance for 2050 scenario

Table 4. Fuel balance for 2050 scenario with the use of regional biomass

S. Di Fraia and L. Vanoli acknowledge the financial contribution of PRIN 2022 Project "AGRoIndustrial sector decarbonisation through energy recovery from waste biomass and integration with other RENEWables”, CUP I53D23001640006, financed by European Union – Next Generation EU, Ministero dell’Università e della Ricerca, Italia Domani Piano Nazionale di Ripresa e Resilienza Missione 4: Istruzione e ricerca.