Combustion behavior of different kinds of torrefied biomass and their blends with lignite Asli Toptas, Yeliz Yildirim, Gozde Duman, Jale Yanik ⇑ Faculty of Science, Department of Chemistry, Ege University, 35100 Bornova, Izmir, Turkey highlights  Torrefaction process improved the reactivity of char combustion step of biomasses.  No interaction between lignite and torrefied biomass at initial step of co-combustion.  Poultry litters can be used as a solid fuel by mixture with lignocellulosic biomass. article info Article history: Received 8 October 2014 Received in revised form 14 November 2014 Accepted 15 November 2014 Available online 3 December 2014 Keywords: Co-combustion Biochar Poultry litters Biomass Kinetic abstract In this study, the combustion behavior of different kinds of torrefied biomass (lignocellulosic and animal wastes) and their blends with lignite was investigated via non-isothermal thermogravimetric method under air atmosphere. For comparison, combustion characteristics of raw biomasses were also deter- mined. Torrefaction process improved the reactivity of char combustion step of biomasses. Characteristic combustion parameters for blends showed non-additivity behavior. It was found that the mixture of torr- efied biomasses and lignite at a ratio of 1:1 had a lower ignition and burnout temperature than the coal- only sample. Although no interactions were observed between the lignite and torrefied biomass at initial step of combustion, a certain degree of interaction between the components occurred at char combustion step. Kinetic parameters of combustion were calculated by using the Coats Redfern model. Overall, this study showed that poultry litters can be used as a substitute fuel in coal/biomass co-firing systems by blending with lignocellulosic biomass. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Turkey’s domestic resource potential is 15.4 billion tons of coal and of this total 14.1 billion tons is lignite. And in energy consump- tion, coal has a share of 31.3% of energy consumption (http:// www.enerji.gov.tr/). However, by 2023, government wants domes- tic resources to make up the main share rather than imported nat- ural gas. Because of this, coal is now referred to as the energy source of the future in Turkey. But it is well known that combus- tion of brown coal causes significant greenhouse gas emissions. On the other hand, co-combustion of biomass with coal provides the reducing net CO 2 emissions from coal-based power plants besides it provides the most efficient and inexpensive uses of biomass. Because of the high content of volatiles and low sulfur in biomass, the combustion of biomass with coal also provides in reduction of NO x and SO 2 emissions (Munir et al., 2010a,b). In addition, co-combustion is a very effective way to dispose of waste materials. Much work on co-combustion of coal with various ligno- cellulosic biomasses has been reported in literature, such as cotton stalk (Munir et al., 2010b), forest residues, olive kernel, and wood (Kastanaki and Vamvuka, 2006), fir wood (Tas ß and Yürüm, 2012), wastes from palm oil production (Idris et al., 2012), olive tree prun- ing (Vamvuka et al., 2014), pine sawdust and oat straw (Kubacki et al., 2012). There are technical challenges in co-combustion of biomass with coal in existing coalfired power plants. The most common challenges include: (1) poor grindability resulting in higher grinding energy requirements, (2) low energy density caus- ing flame instabilities in the combustion chambers, (3) low bio- mass flowability and fluidization properties leading to difficulties in feeding biomass into combustors (Sarvaramini et al., 2014). All these downsides cause the difficulty of utilization of biomass. In order to eliminate these downsides, the quality of biomass can be improved by a pre-treatment process, such as torrefaction. Torrefaction is a slow pyrolysis process carried out at low temper- atures, within a temperature range of 200–300 °C. Torrefaction http://dx.doi.org/10.1016/j.biortech.2014.11.072 0960-8524/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel./fax: +90 232 3888264. E-mail address: jale.yanik@ege.edu.tr (J. Yanik). Bioresource Technology 177 (2015) 328–336 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech