Optimal Control of Multi-Supplier Inventory Management with Lead Time

In the current global competition, companies are required to save money in order to survive. One of the expenses that can be reduced is the cost of inventory control. To minimize these costs, we require a proper planning and management of the inventory. Ordering supplies should be performed at a certain time period, especially with uncertain demand. As such, the company must determine when to order at the suppliers and how many should be ordered. So there will be no excess inventory in the warehouse because of too much ordering or because of the inventory cannot meet demand due to late or too little order to suppliers. Consequently, in this research, a quadratic cost functional is used as the objective function in multi-supplier inventory management problem with different lead time. Optimal control theory, LQR (Linear Quadratic Regulator) is used to solve this problem. According to the simulation, we conclude that the smaller weight resulted in more optimal inventory cost

Technological appropriateness of biomass production in rural settings:Addressing water hyacinths (E. crassipes) problem in Lake Tondano, Indonesia

Climate change has induced an excessive growth of water hyacinths, which produces unintended consequences for the surrounding ecosystem. Particularly, water hyacinth is a major problem throughout the world's tropical zone, which largely consists of rural regions. One way to address the water hyacinths problem is to convert them into biomass. However, typical biomass production technologies have not considered local settings when they are installed in rural areas lacking knowledge and resources. This study aims at assessing the technological appropriateness of biomass production from water hyacinths in rural settings under limited resources and knowledge. This research proposes two scenarios (i.e., high-tech and low-tech) to utilise water hyacinths from Lake Tondano, Indonesia, as the case study. The scenarios consider local settings of communities living around the lake by applying scenario-based design science according to Weiringa's adaptation of the five-stage regulative cycle of Van Strien. The assessment stage employs three levels of technological appropriateness (techno-economic, environmental, social) to assess each scenario for the rural context. Results show that the low-tech design is more appropriate for rural settings around Lake Tondano. Both designs are technically able to resolve the water hyacinths problem; however, the low-tech design is more practical for local communities, addressing the environmental problem while simultaneously boosting socioeconomic developments. In general, the small-scale nature of the more appropriate design applies to other rural areas, with which those areas can utilise various biomass sources while benefitting their socioeconomic situations. Further studies need to assess the technological appropriateness of the appropriate design again based on rural contexts in their location(s)

Supplier selection and operation planning in biomass supply chains with supply uncertainty

International audienceBioenergy is considered a potential solution to reduce carbon footprint and fight against global warming. However, uncertainty in the harvest of biomass could lead to the instability of feedstock supply that has a significant impact on the sustainability of biomass supply chain. In this paper, we present a two-stage stochastic programming model dealing with supplier selection to stabilize feedstock supply of a biomass supply chain in uncertain environments. The model involves the first stage decisions for the supplier selection and the second-stage decisions for planning transportation, inventory and production operations. To reduce the computational burden for large instances, we propose an enhanced and regularized L-shaped decomposition algorithm to solve the model. The applicability of this model and the performance of the solution method are evaluated by numerical studies. Sensitivity analysis shows that the values of some parameters related to suppliers have significant impacts on the optimal expected cost and supplier selection

Investigating the production of multiple bio-products from cassava peel and date seed through an Integrated biorefinery approach

The environmental damage from fossil fuels due to harmful emissions and the desire to find alternative sustainable energy sources led to this investigation of utilising biomass energy. Food wastes are considered one of the important sustainable sources of energy. Exploiting them in the production of energy may lead to avoiding the damage resulting from their accumulation. In this study, the possibility of exploiting the waste/unused product from cassava and date were explored as they are an important food used by many nations. Globally about 550 million metric tons of cassava and 9 million tons of dates are produced annually. Several bio-products can be produced from cassava peel starch and date seed oil, in addition, biogas can be produced through the anaerobic digestion process. The cassava peels have a considerable amount of starch and date seeds contain oil, so this study aims to explore the effect of starch and oil extracted from them on the quantity and quality of the resulting biogas. It also contributes to demonstrating the possibility of benefiting from producing bio-products from extracted starch and oil such as adhesive, biodiesel and glycerine. Overall this research has investigated the production of multiple bio-products from cassava peel and date seed using an integrated biorefinery approach. Cassava peel was treated by beating pre-treatment process to chop and slice the peel and extract the starch at the same time. The date seeds were treated using a grains and stones grinding machine. The digestate resulting from the anaerobic digestion was tested to determine starch and oil extraction effects on the resulting digestate. The influence of temperature, volatile solid and sludge quantity were investigated with the aid of Design of Experiments (DOE). An optimisation process was carried out to calculate the energy balance at the optimal results and evaluate the impact of the extraction process on the biogas and digestate produced, calculating the production costs of biodiesel, the adhesive and the preliminary analysis of process boundary, thus to evaluate its biorefinery applications. The study revealed that the influence of the starch on the biogas quantity and quality was quite low. Simultaneously, the oil extraction process contributed to the decrease in the amount of biogas and methane. The addition of cassava peels and date seeds before and after starch and oil extraction contributed to increase biogas and methane yields. The highest biogas volume obtained from the cassava peel, date seed and extracted oil date seed was 3830 ml, 4140 ml and 3534 ml respectively. The maximum methane per gram volatile solid added was 850 ml /g-VS, 1143.8 ml /g-VS and 949.6 ml /g-VS respectively. The percentage of oil extracted from date seeds was approximately 16% of the date seed weight, while the biodiesel and glycerine accounted for 79% and 9% of it. The starch- based adhesives showed high adhesion strength to the plywood and paperboard specimens. The laboratory tests of the resulting digestate proved that the anaerobic digestion process contains the necessary elements in fertiliser, so this test aims to gain more knowledge about the digestate. Overall, the study investigated the feasibility of an integrated biorefinery approach to the use of cassava peel and date seeds; to produce several bio-products and proper waste management with promising results

Agilité des procédés de transformation de la matière dans un contexte d'approvisionnement et de demande instables : application au traitement de la biomasse

Dans un contexte industriel instable où l’offre et la demande sont incertaines, les industries de procédés sont poussées à transformer leurs systèmes de production. Ce défi s’inscrit dans une transition globale intégrant les exigences liées au développement durable et portée par des tendances fortes. En effet, cette transformation doit tenir compte de la notion de services qui s’installe durablement dans l’industrie. Par ailleurs, l’intensification de la digitalisation impulsée par les technologies de l’Industrie 4.0 créé de nouvelles perspectives d’organisation des moyens de production. À cet effet, les communautés scientifiques du Génie des Procédés, telle que la Société Française du Génie des Procédés, s’accordent pour le développement d’une Usine du Futur. Les enjeux auxquels elle devra répondre sont multiples. Non contente de développer une approche incluant l’économie circulaire, l’industrie de procédés de demain sera numérique et virtuelle. De plus, elle devra adapter l’ensemble du système de production aux fluctuations de son environnement, tout en considérant l’acceptabilité sociale. Dans cette perspective, les initiatives actuelles proposent des solutions reposant majoritairement sur la flexibilité des opérations unitaires ainsi que la modularité du procédé pour une matière première et/ou un produit final fixé. Cela induit des investissements conséquents que ce soit dans les pilotes de laboratoire ou encore la conception d’unité de fabrication. Pour remédier à ces difficultés, l’agilité des systèmes de production apparaît comme une solution, dépassant les concepts de modularité et de flexibilité déjà mis en oeuvre dans ce domaine. Toutefois, il est constaté une absence de conceptualisation et de méthodes de mise en oeuvre de l’agilité dans la discipline du Génie des Procédés. Ces travaux de thèse visent à combler ce manque en proposant un cadre méthodologique outillé pour l’apport d’agilité à l’ensemble de la chaîne de transformation de la matière. Ainsi l’agilité, telle que proposée, permet de comprendre non seulement la dynamique du procédé dans son environnement mais aussi de mobiliser des moyens de production adaptés, en cas de fluctuations. L’objectif de ces travaux de thèse est de construire une chaîne de transformation de la matière supportée par une usine virtuelle résultant de la collaboration de services offerts par des acteurs à l’échelle d’un territoire. Un service de transformation permet de réaliser tout ou partie des étapes du procédé retenu, et est sélectionné selon les besoins. Le procédé est décentralisé en s’appuyant sur des installations existantes afin de s'adapter à la variabilité et à la dispersion de l'offre (mise en oeuvre, exploitation). Dans cette perspective, la première étape de ces travaux de thèse consiste à concevoir un méta-modèle de l’environnement du procédé (acteurs, services, contexte, objectifs et performance). Un second méta-modèle est ensuite proposé pour représenter la connaissance sur les procédés décrits dans la littérature. Sur la base des résultats précédents, la troisième étape s’intéresse à la création d'un algorithme de déduction de la chaîne de transformation de la matière, intégrant les services logistiques nécessaires à sa bonne réalisation. Cet algorithme a donné lieu à la réalisation d’une preuve de concept logicielle. L’usage de ce cadre méthodologique et outillé sera illustré dans le cas de la transformation de la biomasse, à l’aide de données réalistes. En effet, le bioraffinage est l’une des principales voies proposées pour mener la transition énergétique. Cependant, le système actuel de traitement de la biomasse, figé et hautement spécialisé, doit faire face à une grande variabilité en raison de plusieurs contraintes internes et externes (qualité, quantité, pureté, etc.). Pour faire face à cette instabilité, il est nécessaire de faire preuve d'agilité tant en termes de procédé de transformation que d’acteurs et de réseaux logistiques