Hydrothermal carbonization (HTC) of cow manure: Carbon and nitrogen distributions in HTC products

TLDR

The study evaluates the fuel, fertilizer, and nutrient recovery potential of hydrothermal carbonization products derived from cow manure. Cow manure was hydrothermally carbonized at 180–260 °C for 5 and 30 min, and mass and elemental balances were performed for each condition. Compared to lignocellulosic biomass, cow manure shows lower reactivity in HTC, yet the hydrochar’s HHV rises to 22.1 MJ/kg and its NPK ratio is about 20:20:3, phosphorous and other minerals are absorbed into the char, the liquid phase is slightly acidic to neutral containing organic acids, sugars, and amino acids, and roughly half the nitrogen and most potassium are dissolved. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1002–1011, 2016.

Abstract

In this study, cow manure was hydrothermally carbonized (HTC) at 180°C–260°C for 5 and 30 min. Mass and elemental (carbon and nitrogen) balances were performed for each HTC reaction condition. Fuel, fertilizer, and nutrient recovery potential of HTC products are evaluated and discussed. In terms of mass loss, dehydration, and energy densification, cow manure is shown to be relatively less reactive than lignocellulosic biomass in HTC. Ash‐free HHV for hydrochar increased up to a maximum of 22.1 MJ/kg from 19.1 MJ/kg. NPK values of the hydrochar are approximately 20:20:3. Significant amounts of phosphorous and other minerals were absorbed by the solid char from the liquid phase during reaction between 5 and 30 min reaction time. HTC process liquid pH was slightly acidic to neutral, and contains organic acids, sugars, and some amino acids. About half of the nitrogen and most of the potassium are dissolved in the liquid product. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1002–1011, 2016