Cassava processing wastewater as a platform for third generation biodiesel production

ABSTRACT This study aimed to evaluate third generation biodiesel production by microalgae Phormidium autumnale using cassava processing wastewater as a platform. Experiments were performed in a heterotrophic bubble column bioreactor. The study focused on the evaluation of the bioreactor (batch and fed-batch) of different operational modes and the analysis of biofuel quality. Results indicate that fed-batch cultivations improved system performance, elevating biomass and oil productions to 12.0 g L−1 and 1.19 g L−1, respectively. The composition of this oil is predominantly saturated (60 %) and monounsaturated (39 %), resulting in a biodiesel that complys with U.S., European and Brazilian standards. The technological route developed indicates potential for sustainable production of bulk oil and biodiesel, through the minimization of water and chemical demands required to support such a process

Stability of flows associated to gradient vector fields and convergence of iterated transport maps

In this paper we address the problem of stability of flows associated to a sequence of vector fields under minimal regularity requirements on the limit vector field, that is supposed to be a gradient. We apply this stability result to show the convergence of iterated compositions of optimal transport maps arising in the implicit time discretization (with respect to the Wasserstein distance) of nonlinear evolution equations of a diffusion type. Finally, we use these convergence results to study the gradient flow of a particular class of polyconvex functionals recently considered by Gangbo, Evans ans Savin. We solve some open problems raised in their paper and obtain existence and uniqueness of solutions under weaker regularity requirements and with no upper bound on the jacobian determinant of the initial datum

Measure-valued solutions of nonlinear parabolic equations with "logarithmic diffusion"

We prove the existence of a Radon measure-valued solution for a class of nonlinear degenerate parabolic equations with a "logarithmic diffusion" when the initial datum u (0) is a bounded Radon measure, and we study the regularity of these solutions. In particular, we prove that a regularizing effect appears if the initial datum is diffused with respect to the "C (2)-capacity" since in this case the solution becomes a summable function. Finally, we study the uniqueness of these measure-valued solutions

Porous media equations with two weights: smoothing and decay properties of energy solutions via Poincaré inequalities

We study weighted porous media equations on Euclidean domains either with Dirichlet or with Neumann homogeneous boundary conditions. Existence of weak solutions and uniqueness in a suitable class is studied in detail. Moreover, smoothing effects are discussed for short time, in connection with the validity of a Poincaré inequality in appropriate weighted Sobolev spaces, and the long-time asymptotic behaviour is also studied. In fact, we prove full equivalence between certain smoothing effects and suitable weighted Poincaré-type inequalities. Particular emphasis is given to the Neumann problem, which is much less studied in the literature, as well as to the case of R^N when the corresponding weight makes its measure finite, so that solutions converge to their weighted mean value instead than to zero. Examples are given in terms of wide classes of weights