## 1 Introduction  
Agricultural residues, specifically temperate cereal and legume straw biomasses as sub-products of grain production, are surely a potential renewable feedstock for local bioenergy production with potential application in electricity and heat production and in second-generation fuels as well [1]. Traditionally, straw biomasses have been a feedstockconsidered for combustion, torrefraction, gasification, and carbonization technologies, along with fermentation. These biomass applications contribute thereby to a better equilibrium of greenhouse gas emissions from fossil sources and mitigation of climate change effects. In Portugal, the development of cultivations of cereals can be envisaged as very relevant, insofar as the ratio of import/export of the country is 18%. Also, considering the set of wheat, rye, oat, barley, and corn, the degree of self-provisioning in the country is about 20%. The national area planted with grain cereals suffered a substantial decrease (above 70% on average) since 1986. Notably, wheat occupied more than 300 thousand hectares, with this area gradually decreasing, being less than 40,000 hectares in 2016, although with higher productivity by unit area [2; 3; 4; 5; 6]. The Alentejo region in Southern Portugal concentrates currently most of the production areas of these feed cereals, with about 80% of the total productive area in the country, being an important provider of food products, based on temperate cereal and legume cultivations aiming grain production with a huge yield of biomass from shoot straw residues [7; 8]. Alentejo displays a vast undulating and open rolling plain area of about 27,330 km\({}^{2}\), with Mediterranean characteristics and agricultural property specificities in terms of significant areas of individual farms ranging up to tens or hundreds of hectares. This region is also very energetically dependent with a total energy consumption in 2022 of about 143,800 TJ vs. a production of circa 24,500 TJ [9]. Genetic breeding during the second half of the 20 th century led in Australia to gains of 0.015 per decade of temperate cereals in harvest index, HI, defined as the ratio of the grain to the shoot dry matter and of 0.02 in the UK. Traditionally, straw biomasses have been a feedstock considered for combustion, torrefraction, gasification, and carbonization technologies, along with fermentation. Typically, power plants and district heating plants use rectangular big straw bales, which can weigh as much as half a ton with a 2.75 m length and a section of about 1.25 m\({}^{2}\). In the Portuguese textile industry, the use of woody biomass instead of natural gas in steam boilers was shown as competitive with savings of 35% by kWh of thermal energy [10]. The average net calorific value for cereal straws, which is usable for combustion purposes, ranges between 16.6 MJkg\({}^{-1}\) and 20.5 MJkg\({}^{-1}\), with established industrial mature thermochemical solutions ranging between the following: (i) combustion industrial units as large as, e.g., 150 MWe to 350 MWe with co-firing with pulverized coal, with up to 10% and 20 tonsh\({}^{-1}\) of straw share at full boiler load [11]; and (ii) organic Rankine cycle (ORC) cogeneration units of heat and power with less than 1 MWe power and up to 70% of heat yield, corresponding to up to a supply of a 50 tonsday\({}^{-1}\) order or magnitude [12; 13]; or (iii) boilers for heat production of a smaller scale of 125 kW and energetic efficiency of about 75%, used for hot water supply [14; 15; 16; 17]. Straw-heating equipment can be used for heating agricultural facilities, e.g., for livestock, stables, and grain-drying plants. In Europe, in 2019, there were about 370 biomass ORC units [13]. One study showed that in Italy for rice straw, an optimal small-scale ORC solution was based on the production of 100 kWe power and up to 710 kWh thermal energy [18].