IWWG Task Group on
Waste Biorefinery

TG Leaders: Aldo Muntoni / Luca Alibardi

Backround

Direct landfilling of biowaste represents a critical issue, due to the numerous well-known environmental impacts that, in addition to relevant land consumption, are related to disposal of biodegradable residues, including: poor geotechnical properties and mechanical instability, production of relevant amounts of low quality biogas and high-organic load leachate, emission of odors, etc.. The combustion of the organic matter, although allowing for recovering part of the energy content of the waste, is adversely affected by the low heating value and may require complex systems for the purification of the flue gases. Composting represents a well assessed and reliable process for biowaste valorization; however its application is often hindered by energy shortcomings, mainly linked to the costs of the treatment, which mainly derive from the need for mechanical pre-treatment and for forced aeration during the biological stage.
The identification of appropriate strategies for biowaste treatment is thus claimed.
The progressive implementation of the circular economy concepts, the population growth and associated concerns in terms of availability of non-renewable resources, the will of many countries to diversify their strategic sources and to free themselves from the supply of materials and energy resources from areas politically and socially unstable, the fight against climate change, the need to favor delocalization of production systems and promote regional and rural development, the improvement of the knowledge of the factors that govern biological processes, entail that the context of biowaste management currently looks at more ambitious and articulated targets which find the most appropriate and complete synthesis in the concept of waste biorefinery.
The potential inherent in biorefineries is huge. The global industrial production of organic chemicals accounts for a major share of the overall global chemicals industry. The primary outputs of the chemical industrial activity are represented by a relatively limited number of building blocks used to produce a plethora of end products such as food and beverages, pharmaceuticals, pesticides, agrochemicals, water treatment, crop protection, personal care products and cosmetics, fertilizers, automotive industry, gasoline additives, polymers and chemicals, etc. Each building block can also be obtained from biomass, enabling the supply of raw materials at the local level, releasing the industrial activity from expensive and risky supplies, and opening the door to economic sustainability even in disadvantaged contexts. The demand for bioproducts from renewable sources is estimated to reach unprecedented levels with a growth rate of 15%/year.
The concept of biorefinery is not new in its more traditional meaning, and has evolved over time driven by three pivotal aspects:

• cascade approach;
• economic sustainability.
• environmental sustainability;

The cascade approach involves the flexible integration of different processes aimed at producing a mix of biofuels and bioproducts. The integration of processes and products according to the traditional or inverse cascade, is basically linked to economic sustainability, which requires an appropriate mix of products characterized either by significant market sizes - typical of biofuels - or high added values, but also to environmental aspects. In fact, as the number of usable and marketable outputs increases, this would logically correspond to less waste production, thus approaching the zero waste concept.
The improvement in environmental sustainability is the main element underlying the hypothesis of transition towards a new generation of biorefineries: waste biorefineries. The environmental sustainability of the first and current biorefinery generations was, and still is, linked mainly to benefits related to the reduction of the consumption of non-renewable resources and CO2 emissions. The use of residual biomass would bring further environmental benefits:

• first, the environmentally sound management of residues through their valorisation;
• waste biomass should not be grown/bred, leading to a reduction in production costs; no biomass for food use would be treated nor areas that could be dedicated to other uses would be occupied;
• the economic budget would benefit also from the waste treatment fees and short supply chain, besides the sale of the obtained bioproducts;
• the different environmental and economic dynamics that would characterize waste biorefineries could make sustainable process schemes characterized by greater simplicity and smaller plant size as compared to traditional biorefineries.

The concept has faced a growing interest in recent years as demonstrated by the increasing trend of scientific papers published in the field (Figure 1).

Figure 1: Number of published papers on biorefinery over the last decades. (Scopus search, keyword used: “biorefinery”).

As for the processes to be applied, it is important to emphasize the pivotal role that fermentation would play in a waste biorefinery scheme, due to its ability to hydrolyze and simplify the organic substance and convert it to marketable products or building blocks. Indeed, the number of building blocks attainable through fermentation is remakable. Among the marketable products, over the last decades biological hydrogen production has arised a growing interest (Figure 2). The production of bio-hydrogen from organic residues could in fact well fit a sustainable energy economy combining use of hydrogen, electricity and batteries to serve as both energy carrier and storage systems. In this strategy hydrogen can be produced from renewable sources with decentralized on-site small scale plants to both minimize the problems related to storage and transport and to match the wide distribution of feedstock.

Figure 2: Number of published papers on fermentative hydrogen production from waste over the last decades. (Scopus search, keywords used: “hydrogen” AND “fermentation” AND “waste” NOT "photofermentation”).

However, fermentation is a complex process, in particular when applied to substrates which are heterogenous and contain indigeneous microorganisms, and strongly depends on numerous and interconnected factors such as substrate chemical composition, concentration and pretretament methods, presence/type of inoculum and eventual pretreatment, inoculum- to substrate- ratio, reactor type and operation regime, applied operating conditions (e.g., pH, hydraulic  and cell residence time, temperature, organic loading rate, etc.). Therefore, there is still a strong claim for better understanding the complex interrelations among the relevant factors and, in turn, predicting the evolution of the process and optimizing its performance when has to be applied to residual biomass.
Despite the potential advantages highlighted above, it is not conceivable that all the technological and economic perspectives associable to traditional biorefineries could be fully extended to waste biorefineries, if only due to the nature of the residual biomass, which would be, in most cases, qualitatively more heterogeneous and quantitatively less controllable.
Therefore, the following challenge awaits environmental researchers and technicians: is the biorefinery concept feasible for waste management? and to what extent?

All those interested in waste biorefineries, in the production of biohydrogen from residues and in the application of fermentation processes to the valorization of biowaste, are strongly invited to contact us.

Aims

The Group aims to develop the following issues:

• To promote research in biorefineries and bio-hydrogen production from residues and, in particular, from solid waste, to be considered as the most significant substrate to be valorized, as well as the technologies needed, to be developed specifically with a solid waste feedstock in mind.
• To highlight the technical challenges that are specific to use of solid waste as main substrate
• To facilitate international collaboration and create research funding opportunities
• To organise meetings and workshops between researchers in these fields
• To become one of the main reference groups in these fields to facilitate financial support for workshops and conferences and attract sponsorship.
• To explore whether waste biorefinery and H2 bio-production from waste is a realistic and practical process in the waste management field through economic evaluations
• To explore methods of increasing the rate and yield of products, energy and energy carriers from waste
• To disseminate information on workshops, meetings and conferences through the webpage

Members

L. Alibardi, Cranfield University, UK
Th. Astrup, Technical University of Denmark
F. Baldi, University of Florence, Italy
A. Cesaro, University of Salerno, Italy
W. Clarke, University of Queensland, Brisbane, Australia
R. Cossu, University of Padova, Italy
P. Dessì, Galway University, Ireland
G. De Gioannis, University of Cagliari, Italy
F. Girotto, University of Padova, Italy
M.C. Lavagnolo, University of Padova, Italy
L. Lombardi, Niccolò Cusano University, Rome, Italy
A. Muntoni, University of Cagliari, Italy
I. Pecorini, Florence University, Italy
A. Pivato, University of Padova, Italy
A. Polettini, University "La Sapienza", Rome, Italy
R. Pomi, University "La Sapienza", Rome, Italy
R. Raga, University of Padova, Italy
R. Rafieena, University of Padova, Italy
A. Rossi, University "La Sapienza" of Rome, Italy
A. Spagni, ENEA - Italian National Agency for New Technologies, Energy and Sustainable Economic Development
D. Spiga, University of Cagliari, Italy
R. Stegmann, Hamburg University of Technology, Germany
N. Wieczorek, Hamburg University of Technology, Germany

Last event:

Workshop "Waste Biorefinery: Opportunities and Perspectives" during the Venice 2018 Symposium. For a workshop report click here.

Last meeting:

Venice 2018 - Seventh International Symposium on Energy from Biomass and Waste, Venice - Italy, 17 October 2018.

Next meeting:

Sardinia 2019 - Seventeenth International Waste Management and Landfill Symposium, Forte Village Resort, Santa Margherita di Pula (CA) - Sardinia - Italy - 30 Sept-04 Oct. 2019. Proposals for papers and workshops are welcome.

Contact:

Aldo Muntoni (e-mail: amuntoni(AT)unica.it )