## 1 Introduction  
Thermochemical processes such as combustion, pyrolysis, torrefaction, gasification, liquid hot water extraction (LHW), hydrothermal carbonization (HTC), liquefaction (HTL), or gasification (HTG) are some of the most common methods used to chemically transform biomass into energy and chemical products by using heat in biorefineries [1]. Among all thermochemical processes, HTC has gained considerable attention due to its inherent advantages, such as the use of water as a reaction medium, which explains why there is no need to dry the biomass at the beginning of processing, reaction times in the range of 5 min to several hours, lower reaction temperatures (in the range 180-280 \({}^{\circ}\)C) compared to other thermochemical processes, which also means that it is a safer process to conduct experimentally, and the high yield of carbonaceous solids [2]. HTC, also known as hydrous pyrolysis, is carried out by heating a mixture of biomass with a specific ratio of water under subcritical conditions to potentially make a practical variety of products such as hydrochar, high carbon content products, value-added products that vary between platform chemicals, fuels, carbon nanospheres, low-cost adsorbents, and soil amenders [3, 4]. This process has not been commercialized yet because several challenges must be overcome, pointing to the main challenge, which is the development of a feeding system that feeds the mixture of biomass with water against the high pressure of the reactor. The most common biomasses used for HTC processes are the organic fraction of municipal solid waste (MSW), sewage sludge, agro-industrial waste, and nontraditional feedstock sources such as wet animal manures, human waste, and sewage sludges, in addition to aquaculture and algal residues [4; 5]. The HTC process is commonly used as a pretreatment stage integrated with other thermochemical processes, which, in continuous operation, would promote the development of biorefineries [1]. Biorefinery is defined as the facility, plant, or cluster of facilities that integrates sustainable biomass conversion processes to produce value-added marketable products like food, feed, materials, chemicals, and energy such as fuels, power, or heat [6; 7]. The technological process in biorefinery aims to jointly apply thermochemical, biochemical, mechanical/physical, and chemical processes to depolymerize and deoxygenate the biomass components, in this case, the pea pod waste, so value-added products are made by a biorefinery approach [8]. Liquid hot water pretreatment, also known as autohydrolysis, is a method used to improve the enzymatic hydrolysis of biomass, leading to the production of free sugars. This process involves treating the biomass with hot water at elevated pressures, which helps to break down the hemicellulose and reduce the recalcitrance of the material. The use of liquid hot water pretreatment for various types of biomasses, including sugarcane bagasse, poplar, and Italian green pepper waste, has been studied to valorize these materials for the production of biofuels and other value-added chemicals [9; 10]. The effectiveness of this pretreatment method has been attributed to its ability to enhance the saccharification of polysaccharides, particularly cellulose, into glucose, making it a promising approach for the efficient utilization of biomass resources [10]. Agro-industrial biomass utilization has gained significant attention in recent years due to its potential to reduce reliance on fossil fuels and address waste management challenges. Biomass, derived from agricultural and industrial processes, is a widely available resource that can be used for various energy needs, such as electricity generation, industrial process heat, and residential heating [11]. The energy potential of biomass in the South Asian Association for Cooperation (SAC) countries is more than 8 billion gigajoules, with potential biogas energy capacity ranging from 51 MW to over 200 MW [12].