Renewable energy has the potential to power the global economy and effective business models will significantly aid this goal, being among the most critical factors in spurring expansion in the energy industry. This paper reviews articles that discuss business models in the renewable energy sector. Longterm economic, social, and ecological stability is concerned. Previous studies have neglected the environmental sustainability of renewable energy business models, focusing on their technical, social, and economic aspects, primarily for energy access. The business models for solar home and pico systems relied heavily on lowering costs through creative payment plans for customers to be commercially viable. The demand for mini-grids requires end users to launch businesses that can leverage electrification initiatives to be commercially viable. The success of a mini-grid depends on the average consumption and revenue per user. Affordability, unmet energy needs, low electricity demand, lack of financing, unfamiliar business models, and immature markets have impeded energy access in Indonesia. Our analysis revealed that future studies in this field must include environmental sustainability to provide a complete picture for decision-makers. Renewable energy needs in Indonesia can be achieved through the sustainability domain, policy makers can consult this evidence set.

Robo advisor is a technology that can assist investors in managing their portfolios. In the context of Islamic finance, transactions and business relationships must ensure compliance with Sharia principles in order to preserve wealth and meet needs. The use of robo advisors in this context has not been extensively researched. This study aims to determine the use of robo advisors in Islamic wealth management. The research method used is literature review with a normative approach and descriptive-analytical analysis. The data used are from literature on the use of robo advisors and Islamic wealth management in Indonesia over the past five years. Based on the workings of robo advisors, various benefits and limitations are found in their use. The conclusion of the analysis of maṣlaḥah (public interest), functionality, and the urgency of using robo advisors shows that their use in Islamic wealth management can be considered permissible as a means for retail investors and beginners to safeguard wealth (ḥifẓ al-mâl) by applying filters for Sharia-compliant investment instruments and adhering to prohibitions on riba (usury), gharar (uncertainty), maysir (gambling), and haram (forbidden). The research recommendation is to conduct further research on the technical aspects and algorithms used by robo advisors in selecting Sharia-compliant investment instruments, and a sound framework of supervision and regulation is needed to ensure the compliance of robo advisors with Sharia principles and the protection of investors' interests.

The palm oil industry (POI) generates significant amounts of waste, including calcium carbonate (CaCO₃) from the clay bath system used for the separation of palm kernels from shells. This CaCO₃ waste is often discarded, leading to environmental issues. However, the CaCO₃ can potentially be reused in the clay bath separation process to improve efficiency and reduce waste. To obtain PKO, the kernel is separated from the palm shell using a clay bath unit, where natural CaCO₃ acts as a decanting agent and adsorbent. This wet separation method, involving a mixture of water and CaCO₃ with a density of 1.12 g/mL, generates substantial amounts of saturated CaCO₃ waste that is often discarded into the environment. Therefore, this research aimed to regenerate oil-bound CaCO₃ waste for reuse as a decanter and adsorbent. Three treatments were tested, with CaCO₃ waste-to-water ratios of 1:1, 1:3, and 1:6, under varying pH levels (8, 10, 11, 12) and temperatures (28 °C, 80 °C, 100 °C). The regeneration process was conducted in an open reactor at 450 rpm with a volume of 0.0054 m³, followed by drying and grinding the waste for analysis. The results showed approximately 75.75% oil removal and CaCO₃ regeneration rates between 94.50% and 99.26%, with an increase in density from 1.687 g/mL to 2.467 g/mL. The efficiency of reusing regenerated CaCO₃ waste is 96.87%. When mixed with 25% natural CaCO₃, the efficiency increases to 99.24%. Additionally, a mixture of 50% regenerated CaCO₃ waste and 50% natural CaCO₃ achieves an average efficiency of 99.46% over five consecutive feed additions. This showed that the reuse of CaCO₃ waste regeneration results for the separation of palm shells and kernels has a high potential for application. These findings suggest that regenerated CaCO₃ waste can be effectively reused, offering a sustainable solution for palm oil mills.

The development of fossil energy consumption to catalyze the production of biofuels as renewable energy, especially heat and electricity generation, will raise

This study aims to determine the selling mechanism and to understand the reflection of sharia economic law on the mechanism for selling Non-Fungible Token (NFT)-based digital works/creations on the Opensea Platform. This research includes library research (library research) which uses secondary data consisting of three legal materials, namely primary legal materials, secondary legal materials and tertiary legal materials. This research is a descriptive analysis. The data collected was analyzed qualitatively. The results of this study indicate that the mechanism for selling NFTs on opensea is having a balance of cryptocurrency or Ethereum money through a MetaMask wallet, having an account, owning an NFT work, determining the price, how long will the NFT last last uploading the NFT on opensea. Buying and selling NFT is a little different because it uses blockchain technology and the lens of Islamic economic law for the mechanism for selling NFT at Opensea. Looking at the pillars of sale and purchase, the actual NFT transaction process is not fulfilled, because the value or means of exchange (saman) contains gharar and dharar. . The results of the Ijtima Ulama Fatwa MUI decision stated that the use of cryptocurrency as legal currency is unlawful, because it contains gharar, dharar and contradicts Law Number 7 of 2011 and Bank Indonesia Regulation Number 17 of 2015 so it cannot be used as a transaction tool because in practice there are discrepancy with the pillars of the sale and purchase contract. However, it must be acknowledged that the world continues to develop and technology is increasingly sophisticated, it does not rule out the possibility that one day NFT will be legalized. To show that Islam is salihun likulli epoch wa likulli eat (suitable for all times and places), academic ijtihad must be carried out to answer contemporary muamlah problems in the era of globalization.

The objective of this study was to investigate K₂O/Nb₂O₅as a new potential heterogeneous catalyst for biofuel production. The catalyst was prepared through an impregnation method using K₂CO₃and Nb₂O₅. The K₂O/Nb₂O₅was analyzed by scanning electron microscopy (SEM) and Energy Dispersive X-ray (EDX). The catalyst was tested for biodiesel production. Transesterification was conducted using vegetable oil and methanol on the predetermined operating condition. The highest yield of biofuel was the reach of 98.5% at K₂O loading of 50% on Nb₂O₃and the catalyst loaded of 4 wt.% to oil. In the increasing of potassium loading on Nb₂O₃shows increasing the activity of the catalysts. Potassium, as an active site, plays a vital role in the reaction of vegetable oil and methanol to produce biodiesel. It is a major component and enhance selectivity of the catalyst. Niobium was able to interact well with potassium, and it enhanced the crystallinity and stability of the catalyst. The characteristics of biodiesel, such as density and viscosity, are evaluated to confirm the purpose of catalyst function. The biodiesel characterization showed in the range with SNI standard.