Final Report: Reusable Biodegradable Solvents from BiodieselEPA Grant Number: SU836761
Title: Reusable Biodegradable Solvents from Biodiesel
Investigators: Ott, Lisa , Bayham, Jude , Stone, Janine
Institution: California State University - Chico
EPA Project Officer: Page, Angela
Project Period: November 1, 2016 through October 31, 2017 (Extended to January 31, 2018)
Project Amount: $15,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2016) RFA Text | Recipients Lists
Research Category: Sustainability , P3 Awards , P3 Challenge Area - Materials & Chemicals
The overall goal of this project is to improve biodiesel manufacturing by designing a sustainable solution to the industry’s waste glycerol problem. For every 10 gallons of biodiesel produced, one gallon of the glycerol byproduct is cogenerated. This glycerol is currently viewed as a problematic waste stream. Phase II of the proposed project plans to further test the use of biodiesel waste glycerol in the production of a series of deep eutectic solvents (DESs). DESs are garnering increasing interest as a renewable, recyclable, nonvolatile, biodegradable alternative to conventional volatile organic solvents. The bulk of the chemical research performed with Phase I sought to prepare a suite of DESs from biodiesel-waste glycerol and characterize them by measuring density and viscosity. In addition to performing the chemistry necessary to produce DESs from waste glycerol, this project evaluates the potential of using these DESs in research laboratories at California State University, Chico (CSU, Chico) as an alternative to purchasing solvents.
In Phase II, we will build on the success of Phase I. This entails preparing a wider variety of DESs, evaluating their utility as a solvent for a number of organic reactions, determining the optimum composition of the DESs for maximum benefit in the laboratory with minimum cost, and modifying existing teaching laboratories to substitute traditional organic solvents with these DESs. In order to meet the solvent volume requirements of the teaching labs, we will modify our existing protocols to use biodiesel-waste glycerol prepared on site at Sierra Nevada Brewery. As the chemistry student team is working to develop the DESs, the economics student team will develop a cost-benefit analysis to quantify savings for creating and using DESs within the California State University system versus purchasing solvents. We will expand the Phase I analysis by using survey methods to evaluate the nonmarket benefits of reducing the use of volatile organic solvents.
Prior to our U.S. Environmental Protection Agency People, Prosperity and the Planet (P3) grant, our lab published the first report of DESs prepared from biodiesel-cogenerated glycerol and choline chloride. In the short timeframe of the Phase I grant, we furthered our investigations of DESs prepared from biodiesel-cogenerated glycerol. In these studies of DESs, there were two components: the hydrogen bond donor (HBD), which was consistently glycerol, and the hydrogen bond acceptor (HBA), which was one of four different salts. We examined the use of cogenerated glycerol from an acid-catalyzed (AC) biodiesel synthesis; additionally, we prepared DESs using pure glycerol with the new HBAs for reference.
The HBAs triethylamine·HCl, triethylmethyl ammonium chloride and acetylcholine chloride formed liquid mixtures with waste glycerol in all ratios from 5–35 weight percent. Ammonium chloride, however, formed a solid in all weight percents above 10 percent; consequently, we abandoned evaluating it. Density measurements were made on DESs prepared with the three remaining HBAs in DESs made from both pure glycerol and waste glycerol. While there is a deviation from linearity, all of the measured densities were lower than that of the initial glycerol density. Therefore, we have strong evidence for the formation of DESs using these simple, inexpensive HBAs.
Undergraduate students in Principal Investigator Ott’s chemistry class transferred the DESs processed from glycerol produced from an acid catalyzed biodiesel synthesis to a base catalyzed biodiesel synthesis (the latter being significantly more common in industrial biodiesel preparation). Purification of the glycerol from base catalyzed biodiesel synthesis was accomplished using a six-step method: acidification with phosphoric acid, phase separation, neutralization with a strong base, removal of water, methanol extraction and filtration through a short column of activated carbon. While this method was an effective method for purifying base catalyzed glycerol, it does not meet the established tenets of green chemistry. During the course of this evaluation, the chemistry students determined that glycerol produced from biodiesel synthesis using a potassium hydroxide catalyst (instead of the more commonly used sodium hydroxide catalyst) is more amenable to DES formation.
Our Phase I proposal detailed a collaboration with a small-scale, local producer of biodiesel. Our plan was to gather their cogenerated glycerol stream, characterize it, and prepare DESs with this cogenerated glycerol as the HBD. However, after proposal submission (but before the grant was funded), this producer shut down its biodiesel production arm. Consequently, we shifted our focus to producing DESs that could be used in the organic chemistry teaching laboratories at CSU, Chico. The economics student team created a spreadsheet-based model that could be used by a university or a biodiesel producer to determine potential profits from selling DESs as a biodiesel co-product. They also determined that DESs can be produced at a cost lower than the cost of commonly used solvents, indicative of a large potential market for their use.
Annually, the organic chemistry teaching labs at CSU, Chico use approximately 18 L of diethyl ether, 20 L of hexanes, and 20 L of ethyl acetate on an annual basis. These solvents must be disposed of at costs ranging from $6.60 to $990 per liter. Alternatively, DESs can be reused by the University laboratories for up to 5 years before disposal (at the same cost as the traditional solvents). Thus, we are investigating whether production of DESs will yield net benefits to the University over a 5-year time horizon when compared with traditional solvents. Four chemicals were tested as potential inputs to DES production: triethylamine (99% pure), triethylamine (reagent), acetylcholine chloride and choline chloride. Each of the potential input salts can be added to waste glycerol to create DESs; use of higher concentrations of salts improves the physical and electrical properties of created DESs but also increases costs in proportion with the salt concentration.
Our team was able to successfully prepare the proposed suite of DESs using both pure glycerol and acid catalyzed glycerol from biodiesel synthesis. These DESs were characterized by density and viscosity measurements, and the density measurements confirmed that we were able to prepare DESs instead of simple mixtures. Also, a prototype organic reaction was carried out to investigate the solvent properties of the new DES mixtures. Seven undergraduate chemistry majors participated in this project as part of their capstone integrated laboratory, expanding the impact of the P3 funding. Although our small business partner Springboard Biodiesel went out of business before the grant period began, we were able to transition to a profitability analysis using CSU, Chico’s Organic Chemistry teaching labs as an exemplar. Our student team determined that though profitability varies depending upon inputs and input concentration used in production, economic analysis shows that DESs yield cost savings. We found that DESs yield cost savings by year 3 in our most conservative scenario, and by year 1 if the DESs that are produced using lower salt concentrations prove to have the desired chemical properties.