Applied Energy 239 (2019) 471–481 Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy Feasibility study of an off-grid biomethane mobile solution for agri-waste T ⁎ Laura Gil-Carreraa, , James D. Brownea, Ian Kilgallona, Jerry D. Murphyb,c a Gas Networks Ireland, Gasworks Road, Cork, Ireland b MaREI Centre, Environmental Research Institute, University College Cork, Ireland c School of Engineering, University College Cork, Ireland HIGHLIGHTS GRAPHICAL ABSTRACT • Mobile upgrading of biogas from a number of small digesters was as- sessed. − • Upgrading costs €0.62 Nm 3 bio- methane for a mobile upgrading − system (250 Nm 3). • The cost slightly increases with in- creasing number and decreasing size of digesters. • Mobile upgrading was assessed as − €0.18 Nm 3 biomethane cheaper than onsite upgrading. − • A minimum revenue of €1.10 Nm 3 biomethane is required for financial sustainability. ARTICLE INFO ABSTRACT Keywords: Research shows that gas grid injection of upgraded biogas is very advantageous in maximizing energy recovery. Biomethane However, the majority of farms are more than 10 km away from the gas network in Ireland, therefore trans- Off-grid porting biomethane by road to suitable injections points on the gas network would maximize the mobilization of Mobile solution potential biomethane resources. This represents both a challenge and an opportunity in getting to market. A Storage model was developed to describe an off-grid biomethane virtual pipeline solution (cleaning, upgrading and Natural gas storage mobile units) for small-scale farm biogas plants located at more than 10 km from the gas grid system. The cost for 1 Nm3 of biomethane, transported and injected into the gas grid was calculated between €0.62 and €0.80. The model evaluates different scenarios, which differ in the number and size of biogas plants. Comparisons are made to a traditional upgrading model. The model showed that the off-grid biomethane mobile (virtual pipeline) solution costs are €0.18/Nm3 lower than in a configuration of onsite upgrading plants at a biogas production rate of 150 m3/hour. This solution was found to be critical to the development of the wider biomethane industry in countries where direct access to the gas grid is limited by remote location and/or grid injection capacities in some parts of the network capacity. ⁎ Corresponding author. E-mail address: [email protected] (L. Gil-Carrera). https://doi.org/10.1016/j.apenergy.2019.01.141 Received 19 May 2018; Received in revised form 18 November 2018; Accepted 19 January 2019 0306-2619/ © 2019 Elsevier Ltd. All rights reserved. L. Gil-Carrera et al. Applied Energy 239 (2019) 471–481 1. Introduction 1.2. Focus of paper 1.1. Rationale for agri-waste utilization The aim of this paper is to examine biogas production of small scale farm sites located at a remote from the gas grid system in Ireland and In Ireland, 53% of natural gas demand is met by UK imports with the feasibility of an off-grid biomethane mobile solution (cleaning, the remaining gas supplied by means of indigenous gas with field re- upgrading, storage and virtual pipeline) that runs between biogas serves and storage [1]. The UK have commissioned over 80 Biomethane plants and delivers the biomethane to a centralized grid injection fa- Network Entry Facilities in the last three years which allows 3.5 TWh of cility. biomethane on the system [2], this was possible due to the Renewable There is very little literature on biomethane mobile solutions where Heat Incentive (RHI). Ireland could significantly reduce the dependency a small-scale upgrading plant and storage are integrated in one mobile on imports if a similar biomethane system/incentive would be estab- unit, providing a transportable upgrading and virtual pipeline model. lished. In addition to the dependency on imports, the Renewable En- Research has been done to analyse the viability of decentralised biogas ergy Directive (2009/28/EC) published in 2009, established European production with a centralized upgrading and injection into natural gas mandatory targets, which requires 20% of all energy to come from grid model; this showed the financial benefit for small-scale biogas on renewable energy sources including a 10% share of biofuels in the farm producers [15]. This study evaluated a centralized upgrading transport sector by 2020. Ireland's target is 16% of gross final con- model through local pipelines from biogas plants with production of − sumption to come from renewables by 2020 [3]. This target should be over 250 Nm3 h 1, however the majority of the small scale biogas farm made up of contributions of 40% renewable energy in electricity (RES- plants in Ireland will have a potential biogas production below − E), 10% renewable energy in transport (RES-T) and 12% renewable 100 Nm3 h 1 [14]. From literature, it is evident that for biogas flow − energy for heat and cooling (RES-H) [4]. Up to date only 27.2% (RES- rates below 250 Nm3 h 1 the unit cost of upgrading increases drama- E), 6.8% (RES-H) and 5.0% (RES-T) have been achieved [5]. Since the tically making small scale biogas upgrading commercially challenging. publication of the 2008 EU Climate and Energy Package 20-20-20, EU The main reason for the high cost for small scale biogas upgrading is a legislation mandates Ireland to reduce by 20% its Green House Gases lack of upgrading technologies designed for smaller biogas flow rates. (GHG) emissions relative to 2005 by 2020 [6]. Ireland's total GHG Historically gas purification technology focused on large scale natural emissions per capita are among the highest in the EU, and almost a gas purification, moreover with increasing renewable energy demand third (32%) come from agriculture [7], fwith ca. 9% from manure for renewable energy supported by government subsidy schemes in storage [8]. Furthermore, the Nitrates Directive (91/676/EEC) aims to many EU countries, manufacturers have focused on developing biogas reduce the amount of nitrogen from farm waste entering Irish waters upgrading technologies for biogas flow rates ranging from 500 to − [5–6]. Due to the dominance of livestock farming in Ireland and high 2000 Nm3 h 1 [16]. AD plant capital and operational cost vary sig- annual rainfall, the country has been designated as a nitrogen vulner- nificantly depending on plant capacity, type (e.g. dry, batch, con- able zone (NVZ) which requires that organic sources of nitrogen, such tinuous) and specification, but smaller plants can still be built and as manure and slurries, must be stored from 16 to 22 weeks during operated relatively cheaply, as is demonstrated by the large number of winter months depending on the region within the country [9]. small-scale plants in China and India [17]. However, the Swedish Gas Processing agricultural waste such as manure and slurry in an Centre [18] highlighted that total biogas cleaning costs for upgrading anaerobic digester is a sustainable method of treating animal manure are considerably higher for smaller plants, especially for plants treating − and is one of the few commercially available technologies that can less than 100 Nm3 h 1 of raw biogas. Therefore, there is a necessity to reduce the GHG emissions from agriculture. investigate models to allow those small scale AD plants to access the Biomethane from wet and dry manure could be GHG negative on a biomethane market. This is critical to the development of the wider whole life cycle analysis (LCA) basis achieving up to 140% GHG saving green gas industry in countries where small-scale biogas producers are due to the additional carbon saved from avoided methane emissions predominant and the physical or economic conditions deem the in- from manure storage [10]. stallation of a real pipeline unfeasible. Hakawati et al. [11] performed an intensive study on the most en- The model proposed in this paper facilitates the integration of ergy efficient route for biogas and it was found that biomethane uses biomethane as a route to meeting renewable energy targets and off- competes well with biogas and is more easily transported and used in a setting reliance on imported oil and gas, as well as offering a solution wide variety of applications. There is a perspective that bioenergy is that can be used to provide a sustainable and cost effective route to better employed in systems, which are difficult to decarbonise. In an market for small scale biogas producers to the gas grid. Irish context industrial heat (such as in breweries, distilleries and The objectives of this paper are to establish: creamery plants) is difficult to decarbonise. On an international basis transport fuel is difficult to decarbonise. Green gas is a decarbonised • What is the cost of upgrading, storing, transporting and injecting substitute for all natural gas applications, in particular in this work for into the gas grid with the mobile solution expressed per Nm3 of transport and heat. biomethane? It was estimated that biomethane production from agricultural • What is the effect of the size and scale of biogas plants on the overall slurry could achieve 15.53 PJ by 2020, which represents 6.4% of the cost and technical feasibility of the mobile solution? estimated natural gas demand in 2017 [12]. Furthermore, the farming • Can a mobile solution (upgrading, storage and transport) on a re- sector is still crucial to Ireland’s economy and the most important in- mote site coupled with a centralized biomethane injection facility be digenous sector. O’Shea et al. estimates that total annual cattle slurry feasible? production in Ireland is approximately 28.9 Mtwwt, which represents • What is the potential of the mobile solution and virtual biomethane 91% of the total theoretical biomethane resources [13].