Profile: WALEVA project – Demonstrating levulinic acid production from rice straw

Type of post: PROJECT PROFILE.

Técnicas Reunidas (TR) is a Spanish multinational known worldwide for being a general contractor, engaging in the engineering, design and construction of various types of industrial facilities for a broad spectrum of customer, mainly, oil and gas companies. However, it is not so well-known, even in Spain, that TR owns a facility where new technologies for different fields are developed: José Lladó Technological Centre. There, clearly, hydrometallurgy is the star. For more than 40 years, the Proprietary Technology Development Division has been establishing a series of in-house metal recovery technologies.

Figure 1. José Lladó Technological Centre (courtesy of TR)

Also, there is room for biorefining processes: transformation of rice straw into levulinic acid, lignin valorization or biobutanol production. Regarding to the first one, TR has coordinated the project WALEVA funded by the Programme LIFE of the European Commission. At the end of last year, Dr. Vicente López (project leader) was kind enough to explain to me the details of this interesting initiative and show me the pilot plant which was deployed to demonstrate the continuous process. Let us deep insight into the project.

The challenge and the proposed solution

Spain is the second rice producing country in the European Union. As we can read on the website of the WALEVA project, there are, approximately, 105,000 hectares destined to rice farming in Spain, this implies the generation of 577,000 tons of rice straw every year. If we extend the scope, the rice production in Europe exceeded 3 million tons in 2012. Taking as a reference an average of 0.8 tons of straw residue per ton of rice, that year 2.4 million tons of residues were generated. The two main operations used to manage this waste (burning and incorporation into the soil) pose an environmental problem. For instance, the burning of the total quantity generated during 2012 would amount to 4.1 million tons of CO₂ into the atmosphere (1.7 kg of CO₂ per kilogram of straw). In the post devoted to the SostRice project (SostRice Project – Searching for a sustainable model of rice straw management, 2/3/2016), I address this issue in greater depth so I will not expand further here.

The partnership of the WALEVA project proposed a solution for this problem supported by the principles of the circular bioeconomy. Their strategy was to pave the way to develop a new value chain based on a high added value product: levulinic acid (LEVA). This molecule is a very versatile platform whose derivatives have potential in many applications: fuel additives, solvents, polymers and plasticisers, resins and coatings… (follow the link to know more: “Levulinic acid biorefineries”). In this way, through the conversion of straw rice into levulinic acid, the use of raw materials and energy resources to produce goods would be reduced while a sustainable solution to manage the waste would be reached.

The project

The general data of the project are summarised in the following table:

Name	WALEVA - From Whatever Residue into Levulinic Acid: an innovative way to turn waste into resource.
Objective	To demonstrate the viability of the production process developed by TR to generate levulinic acid, starting from different types of lignocellulosic residues or from raw materials subject to contain at least a 30-40% cellulose fraction.
Call	LIFE
Reference	LIFE13 ENV/ES/001165
Partnership	Coordinator: Técnicas Reunidas. Partners: - Centro de Investigaciones Científicas y Tecnológicas de Extremadura (CICYTEX). - Federación Empresarial de la Industria Química Española (FEIQUE).
Duration	From 6/2014 to 9/2017.
Total budget	1,633,680 €
EU contribution	816,839 €

The six main actions carried out in order to achieve the general objective are the following:

1. The rice straw residue collection and treatment.

2. A storage module design and construction.

3. The pilot plant design.

4. The pilot plant construction.

5. Demonstration in the pilot plant.

6. Economic, energy and environmental feasibility studies.

During the early months of the project, the first activity centered on the optimization of the rice straw collection was performed. It was fully supported by the Don Benito and area Farmers Association (this zone is the main rice production area in Extremadura and the second production area in Spain). The ulterior actions were focused on the core of the project: the demonstration of the technology developed by TR to produce LEVA from lignocellulosic materials in a pilot plant built in the José Lladó Technological Centre.

The WALEVA process and the pilot plant

The production process is comprised of the following stages:

1. Pretreatment

The first step is a physical (mechanical) chemical (acid attack) pretreatment of the rice straw residue aiming at preparing it for its ulterior acid hydrolysis, ensuring that the downstream hydrolysis performance reach the expected yield rate. A proper selection of the particle size is crucial. Due to this, during the development of the project, different kinds of mills were tested. This pretreatment seeks also to reduce the quantity of possible impurities.

2. LEVA production and purification

2.1 The solid generated is treated through acid hydrolysis with exhaustive pressure and temperature controls. The hydrolysis strive to break selectively the cellulosic fraction in order to create isolated glucose units. Thus, by ulterior conversion in the same aqueous medium and thanks to a dehydration process and ulterior rehydration, the LEVA and formic acid (FA) mixture is obtained. When the final mixture is filtered, a liquid solution rich in levulinic acid is formed and simultaneously a recoverable solid called biochar is produced. This material can be used to obtain energy or other applications.

2.2 The LEVA generated during the acid hydrolysis has to be chilled and purified in several stages to obtain a final product with a 90-95% purity.

Figure 2. Basic flow diagram of the WALEVA process (courtesy of TR)

The pilot plant was built during 2015 and 2016 and the demonstration tests with rice straw were carried out in 2017. The results are shown below:

Processing capacity	500 kg of rice straw per month (700 g of rice straw per hour). 370 kg of rice straw during the test campaign.
Production capacity	150 g of LEVA per hour.
Working flow rates	3 – 4 l/h.
Time in operation	600 hours (5 weeks, 5 days per week, 24 hours per day).
Yield	16% – 18%.

Figure 3. Left: LEVA / Right: Rice straw, crushed rice straw, pretreated solid and biochar (courtesy of TR)

Feasibility study and future plans

Using the data obtained in the demonstration stage, energy, environmental and economic feasibility studies of the process were conducted. Considering Valencia as potential location and the straw generated by the rice production industries of Valencia and Andalusia (624,000 tons), 83,000 kg of LEVA could be obtained and the carbon footprint could be reduced by 80% compared to the burning. Taking into account a price between entre 1.5 €/kg – 2 €/kg of LEVA, the payback time would be around 4 – 5 years.

Therefore, this preliminary analysis delivers results that allow them to be optimistic. At that time, TR is assessing the way to scale-up the process to a precommercial level and searching for partners to develop applications for its LEVA.