Dear Colleagues,

Hydrothermal processing of biowaste has been recently recognized as a promising technology to efficiently reduce waste volume, recover bioenergy and nutrients, destroy organic contaminants, and eliminate pathogens. This Special Issue is focused on all of the technologies that are able to carry out nutrient and energy recovery from any kind of waste (animal manure, municipal waste, organic waste from the industrial food sector, sewage sludge, green waste, among others). Particular emphasis is placed on to those technologies that are currently at a high technological readiness level, thereby including their applicability through techno-economical and life cycle analysis.

Prof. Dr. Angel F. Mohedano
Prof. Dr. Elena Diaz
Prof. Dr. M. Angeles de la Rubia
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Resources is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• waste management
• waste to energy
• hydrothermal treatments
• anaerobic digestion
• dark fermentation
• circular economy

Title: Low Water Input Co-Hydrothermal Carbonization: When One Biomass Can Partially Supply the Water to the Other

Abstract: One drawback of biomass hydrothermal treatment (HTC) is associated to the need of water supply, that is especially important in the case of lignocellulosic low water precursors. In this context, economic and feasibility studies suggest using at least 20-30% of load to water ratio should be provided to guarantee an appropriate biomass conversion but also to satisfy a feasible water balance. This study has investigated the possibility of co-hydrocarbonizing two residual biomass materials that significantly differ in their physico-chemical compositions: a) olive stone, a hard and high quality biomass, with low N content, whose potential to give a high heating value briquete by HTC has been proven, b) fresh grass as it is gathered from gardens, with a high water content, moderate N fraction, and low calorific value. The work specifically focus on the water saving that can be attained, when the liquid product produced by one of them (grass, with a 80% of moisture, that is almost fully recovered under tight heating in the form of acidic liquid solution) can supply part of the water needed by the other (olive stone). The changes in product distribution and HC properties as a result of this process modification are investigated and associated to the synergies found in the processes, comparing isolated treatments with co-HTC.