Activated carbon is highly porous carbon which has been treated to increase its adsorption performance. Rice husk, due to its high cellulose and lignin content, can be used as source of carbons to produce activated carbon. This research aims to evaluate the effects of carbonization time and temperature on activated carbon production from rice husk and its application for lead (Pb) adsorption in car battery wastewater. In this research, dried rice husk was carbonized at 400-600 °C under constant nitrogen flow for 90 minutes to 150 minutes, followed by chemical treatment using HCl. Dried activated carbons was sieved to 100 meshes prior to application. Result indicated that maximum carbon yield of 49.33% was obtained at carbonization temperature of 500 °C and carbonization time of 150 minutes. The activated carbon contained 4.86% moisture, 30.04% ash, and 15.76% volatile matter. The adsorption capacity was found to be 0.56731mg/g with percentage removal 54.85%.

The production of crude palm oil (CPO) in Indonesia is keep increasing that make the amount of wastewater generated. Technology of anaerobic fixed bed (RANUT) have been developed, but the characteristic of the wastewater effluent of RANUT has not meet the quality standard that required by the goverment especially for COD. Because of that need to make a furhter research about the treatment of palm oil mill from the fixed bed reactor (RANUT) with electrocoagulation technique. Electrocoagulation is a process of coagulation by using a direct current through an electrochemical events are symptoms of electrolyte decomposition. This study aims to determine the effect of voltage on the adapter parameters on the performance of the electrocoagulation system and determine the best time for treatment of palm oil mill effluent. Type of electrode material used is aluminum, waste retention time 1 hour, 5 cm distance between the electrodes, a strong current of 5 amperes, voltage variations adapter 3, 4, and 5 volts. The results showed that the best results are obtained at a voltage of 5 volts for COD removal 81.32% with a value 233.5 mg/l at 180 minutes of processing time, it indicates that the processed waste has met quality standards for mill effluent COD is 350 mg/l. The highest turbidity removal percentage is obtained at a voltage of 5 volts and at a time of 180 minutes with the acquisition of 95.08%.

In the framework of integrated pest management, biological control through the use of living organisms plays important roles in suppressing pest populations. In this paper, the complex interaction between plants and pest insects is examined under the intervention of natural enemies releases coupled with sterile insects technique. A set of nonlinear ordinary differential equations is developed in terms of optimal control model considering characteristics of populations involved. Optimal control measures are sought in such a way they minimize the pest density simultaneously with the control efforts. Three different strategies relating to the release rate of sterile insects and predators as natural enemies, namely, constant, proportional, and saturating proportional release rates, are examined for the attainability of control objective. The necessary optimality conditions of the control problem are derived by using Pontryagin maximum principle, and the forward–backward sweep method is then implemented to numerically calculate the optimal solution. It is shown that, in an environment consisting of rice plants and brown planthoppers as pests, the releases of sterile planthoppers and ladybeetles as natural enemies can deteriorate the pest density and thus increase the plant biomass. The release of sterile insects with proportional rate and the release of natural enemies with constant rate are found to be the most cost-effective strategy in controlling pest insects. This strategy successfully decreases the pest population about 35 percent, and thus increases the plant density by 13 percent during control implementation.

Pest insect is one of the major pests that cause damage and loss in agriculture around the world. This threat also comes with other complex problems such as environmental hazards by the indiscriminate pesticide and the rapid development of insects due to the environmental change. Therefore, more environmentally friendly and sustainable control methods need to be implemented. This paper discusses a generic model to describe plant-insect interaction and focuses on the interaction between non-vector pest insect and plant. The model consists of a set of non-linear ordinary differential equations representing insect-plant predator-prey interaction with the addition of two controls, namely green insecticide and mating disruption. An optimal control approach was exploited to solve the control problem and find a set of control strategies that regulate the system optimally. The simulations were conducted for three strategies and four scenarios describing possibilities in the real-world application. Our results suggest that all strategies managed to prevent agriculture loss. A cost-effectiveness analysis was conducted to examine the cost and benefit of applying each strategy.

Travelling Salesman Problem (TSP) is a problem where a person must visit some places, starting from one city and then moving on to the next city with the conditions that the places visited can only be passed precisely once and then back to the starting city. TSP is an NP-hard, an important problem in operations research. TSP problems can be solved by an exact method or an approximation method, namely the metaheuristic method. This research aims to solve the TSP problem with an approximation method called the Simulated Annealing (SA), and then compare the results of this approximation method with the exact Branch and Bound method. The results indicated that the SA method could accomplish TSP problems. However, like other metaheuristic methods, SA only accomplishes it using an approach to get good results. Still, it cannot be determined that SA has the most optimal results, but the time needed by the SA method is faster than the Branch and Bound method. In case I, the percentage difference between the distance generated using the SA method with the B-and-B method is 0%, in case II it is 7% and in case III it is 8%.

Proses distribusi produk yang dilakukan oleh produsen untuk memenuhi kebutuhan konsumen sering kali melibatkan penyelesaian masalah perutean kendaraan. Vehicle routing problem (VRP) dapat digunakan untuk menentukan rute dan alokasi kendaraan agar biaya distribusi minimum. Penelitian ini membahas masalah penentuan rute distribusi beras untuk keluarga sejahtera (rastra) dari gudang penyimpanan Perum Bulog di Kabupaten Ponorogo ke beberapa desa/kelurahan. Periode pendistribusian yang diambil dalam penelitian ini hanya satu dari dua belas periode yang tersedia. Terdapat desa/kelurahan dengan permintaan yang melebihi kapasitas kendaraan, sehingga memerlukan distribusi terpisah. VRP dapat diselesaikan menggunakan metode eksak maupun heuristik. Dalam penelitian ini, metode heuristik yang digunakan adalah algoritma genetika dengan solusi awal diperoleh dari metode nearest neighbour untuk distribusi beras di Perum Bulog. Dari hasil implementasi diperoleh rute kendaraan yang meminimumkan biaya distribusi dan memenuhi semua kendala yang ada menggunakan algorima genetika dan diberikan pula hasil perbandingannya dengan solusi dari metode eksak.